They’re restaurants on wheels, churning out everything from pan-seared dumplings to juicy porchetta sandwiches for the city’s hungry lunchtime crowds.

But food trucks, which are proliferating at a rapid pace around Boston, are more likely to be temporarily shut down for serious health violations than their brick-and-mortar counterparts, most commonly for violating a basic requirement for proper sanitation: running water.

A Boston Globe review of 2016 city health records found that while food trucks were less likely overall than restaurants to have violations, they were more likely to be suspended for serious issues that pose an “imminent public health threat.’’ Nine of the city’s 96 licensed food trucks last year were closed on the spot until the violations were corrected, usually within a week or two. By comparison, two of every 100 restaurants were suspended.

“Food trucks have unique risks compared to regular establishments, additional challenges’’ when it comes to food safety, said Tennessee State Epidemiologist Tim Jones, a national expert in the spread of food-borne illness. “Clean water is extremely important.’’

A recent E. coli outbreak that shuttered several food trucks operated by the Chicken & Rice Guys has raised questions about whether these movable feasts are as safe as traditional restaurants.

Food trucks in Boston were cited for violations 200 times in 2016, and of that total, about half were serious infractions, and the other half minor. A majority of the most serious violations that led to temporary suspensions were related to water, or the lack of it.

On board some trucks, the water tank was empty or a sink or pipe leaked, so employees were not able to rinse vegetables and surfaces or wash their hands, as required by health regulations.

City inspectors closed The Savory Truck outside Brigham and Women’s Hospital in April 2016 after inspectors found condensation dripping into food and no water for employees to wash their hands, according to city inspection reports.

The next day, officials temporarily shuttered Saigon Alley, a food truck specializing in Vietnamese fare in the Financial District. Health inspectors said there was “no evidence of handwashing due to broken pipes at handsink.’’

The Clover food truck parked at Dewey Square was ordered to close immediately last October. Once again, the issue was water.

In 2013, Clover voluntarily pulled its trucks off the road after a salmonella outbreak affected 12 people, at least half of whom ate at one of its restaurants or food trucks. Salmonella bacteria can cause diarrhea, fever, and abdominal cramps, and in severe cases, hospitalization.

Water and hand-washing are fundamental to keeping harmful bacteria at bay in any food establishment, but even more critical on a food truck, said Doug Powell a former professor of food safety at Kansas State University and an author of Barfblog.com, which chronicles food-borne illness outbreaks.

In a small space, washing takes on more importance because bad bacteria can spread more quickly. Cutting surfaces on the trucks are used for a variety of tasks, he said, and workers who serve food might also collect payments.

The rolling restaurants are also not connected directly to a city’s water supply and rely instead on a water tank connected to a sink, much like on a boat or airplane. Water can simply run out, and finding places to refill poses another dilemma, so workers might cut corners to conserve it.

“All of those health problems get magnified in a smaller space on a food truck,’’ Powell said. “So you really have to be good at what you’re doing.’’

The problems have come to light as food trucks soar in popularity. The number of trucks in Boston grew from 14 in 2010 to 96 in 2016.

Trucks generally operate without significant problems, and the industry has long ­argued that they are as safe as — if not safer than — restaurants.

A 2014 report by the Institute for Justice, a public interest law firm in Virginia that advocates for the industry, focused on overall health violations rather than temporary truck closures to assess risks. It found that Boston trucks had fewer violations than restaurants overall, but glossed over the fact that the trucks get virtually the same number of serious violations as restaurants.

Based on inspection reports collected from 2011 through July 2013, the institute said there were 2.7 violations per food truck in Boston, compared with 4.6 violations per restaurant.

An institute spokesman, Rob Frommer, said the report did not analyze closures because the group wanted a broad analysis of food trucks that’s based on routine annual inspections instead of suspensions.

In Boston, a health inspector may cite an establishment for violations, but only the most urgent safety infractions will lead to a temporary suspension warranting a temporary closure.

William Christopher, Boston’s commissioner for Inspectional Services, said he thinks the rate of food truck suspensions means that inspectors are doing a good job identifying problems.

“We’ve been working closely with the food truck people to better inform them of our expectations,’’ Christopher said.

Matt Geller, president of the National Food Truck Association, said one of the best indicators of a food truck’s health safety record is a letter grade issued by local health officials. Such grades are required on all trucks in Los Angeles, he said, and are being rolled out in Boston.

“We see E. coli outbreaks in restaurants, so it’s not about the vehicle or the food,’’ Geller said. “It’s about the particular operation.’’

City officials began scoring restaurants and food trucks in November 2016, and assigning letter grades of A, B, or C.

Consumers can also check out the “Mayor’s Food Court’’ on the city’s website, www.boston.gov/health-and-human-services/mayors-food-court, where the Inspectional Services Department posts its findings.

Yet the letter grades and inspector’s findings tell only part of the story.

Unlike in brick-and-mortar restaurants, where food is usually cooked on-site, food served by trucks is typically made in commissaries or rented kitchens, and loaded on board.

Problems at one of those commissaries came to light recently during a Chicken & Rice Guys E. coli outbreak that sickened 15 people who ate food from its trucks and its Allston restaurant.

Health investigators from the Somerville and state public health departments inspected the Foundation Kitchen commissary after the outbreak and found a rodent infestation. Inspectors also said a garden hose connected to a bathroom faucet was used to fill food trucks’ water tanks. (That is not allowed for several reasons, including that bathroom plumbing has no “backflow’’ prevention device.)

The commissary had also been forced to close for three days in 2015 after inspectors found filthy equipment and a general lack of cleanliness.

Foundation Kitchen’s owner, Ciaran Nagle, told the Globe last month that he would no longer rent commissary space to food trucks, saying it was ill-equipped to handle their needs.

In the meantime, the Chicken & Rice Guys food trucks have not yet returned to the road, although its restaurants have reopened. The source of the E. coli has not been identified.

A Boston food safety consultant, Lisa M. Berger, said the way food trucks move their food between sites, with more people packing and handling the food, creates the potential for more problems.

Berger said while that won’t stop her from eating at her favorite food trucks, she checks the Mayor’s Food Court website to review inspectors’ findings, as a precaution.

“Definitely there are more issues with mobiles,’’ she said of the trucks. “There’s more that can go wrong.’’

200

The number of times food trucks in Boston were cited for violations in 2016. About half were serious infractions.

Megan Woolhouse can be reached at megan.woolhouse@globe.com.