Governor Charlie Baker declared a state of emergency for Massachusetts on Tuesday, as the number of Covid-19 cases in the state more than doubled to 92 and the first cases with no known source broke out in Berkshire County.

Seeking to slow the spread of the virus, Baker announced travel restrictions on all 42,000 employees of the state’s executive branch, banning out-of-state work-related travel and in-person conferences and seminars. He urged other large employers to do the same.

“I would have to say that the risk has increased,’’ Baker said at a State House news conference. “Responding to this evolving health threat requires everyone to be vigilant and everyone to be part of this effort.’’

The Berkshire cases mark a turning point in the outbreak in Massachusetts, because they indicate the virus may be spreading freely in the community. Previously, all the infected people in the state had either traveled abroad or had contact with an infected person, the majority at a conference of Biogen employees.

“Person-to-person spread of the virus is beginning to occur among individuals without identifiable risk factors,’’ said Public Health Commissioner Monica Bharel, saying the focus now shifts from containing the virus’s spread to mitigating it. A health department expert has been dispatched to help with the Berkshire County outbreak, she said. There are seven Covid-19 cases in the county but it was unclear Tuesday how many were of unknown origin.

With this leap to so-called community transmission, the goal becomes slowing the outbreak’s progress so the health care system does not become overwhelmed with too many patients at once, Baker said. “It’s only possible if everybody does their part.’’

Baker said the emergency declaration will “give our administration more flexibility to respond to the developing outbreak,’’ including in quickly finding space to stockpile supplies or, if need be, empowering the governor to cancel large-scale events to help contain the spread of the virus.

He noted that people with chronic health conditions and adults over 60 are at greatest risk of severe illness and death from Covid-19, and urged them to avoid large gatherings — but assured them that MBTA stations, trains, and buses are being regularly cleaned.

Baker noted that he expected to see less of his own 91-year-old father, to protect him. “He and I are probably going to have a lot of conversations over the phone over the course of the next few weeks,’’ Baker said.

Meanwhile, the state will provide new guidance to long-term-care facilities, in keeping with plans by nursing homes and assisted living facilities across the nation to begin screening all visitors and restricting entry to all but essential health care workers.

Baker also said he was easing state rules on school attendance so that officials would feel free to close down schools if need be. He also urged “all districts to cancel out-of-state travel.’’ The state won’t require any to extend their school year past June 30, and the state Department of Early and Secondary Education would disregard any attendance data after March 2.

For now, Baker said, officials are still discussing whether to hold the Boston Marathon on April 20. But he praised the decision to cancel the Boston St. Patrick’s Day parade and said “large gatherings are probably not a great idea.’’ Lawrence has also canceled its St. Patrick’s parade.

“We believe it’s important to start taking more aggressive action now,’’ Baker said. Officials expect “this disruption to continue for the foreseeable future,’’ he added.

Earlier Tuesday, legislative leaders said they intend to allocate $15 million to Covid-19 response efforts, although they didn’t specify where the money would go. Scheduled for a vote next week, the spending package would be the first major infusion of state cash to address the virus.

Baker said he expects the funds to help both the state Department of Public Health and local health boards.

Across the border in Rhode Island, the Department of Health reported Tuesday that a woman in her 50s who traveled to Egypt and a Rhode Island Hospital health care worker in her 30s have tested positive, the state’s fourth and fifth cases.

Of the 92 Covid-19 cases detected in Massachusetts so far, four involve foreign travel, 70 were connected to the Biogen meeting, and 18 are still under investigation. Six people have been hospitalized.

The unknown cases include at least some of the patients in Berkshire County, whose illnesses have already had far-reaching effects. Berkshire Medical Center in Pittsfield is facing staffing shortages after it furloughed dozens of staff members who came in contact with five Covid-19 patients before the sick people could be tested.

According to a hospital spokesman, starting March 1, the patients separately came to the Berkshire Medical Center emergency department with severe flu-like symptoms and were admitted. In each case, the state Department of Public Health did not agree to test the patients for about five days.

During that time, nurses and other employees who were exposed to the patients were placed on a 14-day quarantine as soon as the test results came back. (The nurses had worn masks but not the eye shield and gowns needed to protect against the coronavirus.)

The Massachusetts Nurses Association, a union representing workers at Berkshire Medical Center, said that 70 employees were on furlough, including 54 nurses. The hospital, which has about 800 nurses, remains open.

The hospital acknowledged that staff members had been asked to self-quarantine for 14 days but declined to specify how many or to confirm the union’s numbers.

The union said it has not received any reports of nurses or other health care workers who have been infected with the virus.

Testing capacity in the state is expected to increase rapidly, however, making delays like those experienced in Berkshire County less likely.

The state public health laboratory, currently the only place in the state equipped to test for the coronavirus, is automating an aspect of the testing and expects to increase its capacity from 40 to 50 tests a day to 200 a day, Public Health Commissioner Bharel said at the press conference. The lab has also received an additional 2,000 test kits, she said.

Additionally, private laboratories are working on getting federal approval to start doing the tests.

So far, the state’s lab has completed tests for roughly 400 people and can complete them in 24 to 48 hours, Bharel said.

To meet hospital needs, the state is also expecting to receive supplies through the federal emergency medical equipment stockpile, but did not have specifics of how many gowns, face masks, and other items it will get.

Political officials are also taking precautions. The Massachusetts Democratic Party is temporarily suspending all of its remaining caucuses, the weekend gatherings at which Democrats elect delegates for the state party convention, where they will endorse a candidate in the Senate primary between Senator Edward Markey and Representative Joseph P. Kennedy III, according to chair Gus Bickford.

“In the event that this temporary suspension must continue for an extended period of time, the party will develop a replacement to the caucus process,’’ Bickford said Tuesday. “The party has informed Senator Markey and Congressman Kennedy of this decision, and each supported the necessary decision by the state party to postpone the caucuses.’’

Meanwhile, as calls to avoid needless travel increased, passenger traffic through Logan Airport dropped considerably last week. About 351,000 passengers passed through security checkpoints between March 2 and March 8 — down about 53,000, or 13.2 percent, from the same week a year ago.

Liz Kowalczyk, Danny McDonald,Adam Vaccaro, Robert Weisman, and Edward Fitzpatrick