HALF MOON BAY >> The owners of two San Mateo County mushroom farms where a man allegedly killed seven coworkers in back-to-back shootings last year will pay over $450,000 in back wages and damages to dozens of employees, according to federal authorities.

The settlements follow an investigation by the U.S. Department of Labor that found Concord Farms Inc. and California Terra Garden Inc. violated both the Migrant and Seasonal Agricultural Worker Protection Act and the Fair Labor Standards Act.

The federal agency’s Wage and Hour Division launched the probe in the wake of the January 2023 shootings. A man who lived on one of the farms, 67-year-old Chunli Zhao, is accused of killing fellow employees and is now facing seven counts of murder and one count of attempted murder. He pleaded not guilty to the charges in February.

At California Terra Garden, investigators found 39 workers housed in cramped containers, garages and dilapidated trailers, the Labor Department said in a news release. The employees were forced to sleep on dirty mattresses and exposed to insects and garbage.

The federal agency said the married couple who owned the farm — identified as Xianmin Guan and Liming Zhu — also illegally deducted money from workers’ pay for the substandard housing. An operations manager at Terra Garden declined to comment on the fines.

Employees at Concord Farms, located just two miles away, were found housed in moldy, makeshift rooms in a greenhouse crawling with insects, according to the Labor Department.

The owner of the farm — identified as Grace Tung — shortchanged workers who received the regular rate of pay for all hours worked, including hours over 40 in a work week, and who were also not paid for work off the clock, the federal agency said. Attempts to reach Tung were unsuccessful.

“Our investigators found workers at California Terra Garden and Concord Farms housed in sickening conditions, forced to sleep near garbage and with insects all around,” Wage and Hour Division Assistant District Director Alberto Raymond said in the release.

“The Department of Labor is determined to hold employers accountable when they ignore their legal responsibilities to provide suitable housing when required and pay workers all their legally earned wages for the hard work they do in difficult conditions,” Raymond continued. “We are committed to enforcing these workplace protections that ensure a safe and suitable living conditions for seasonal workers.”

The settlement with Union City-based Concord Farms calls for it to pay a total of $370,107 in overtime wages and liquidated damages to 10 workers, $4,242 in late wages to 23 workers and $29,049 in civil money penalties to address its violations.

California Terra Garden, meanwhile, will pay $84,074 to allow 39 workers to recoup the employers’ illegal housing deductions and $42,494 in civil money penalties to resolve its housing, wage disclosure and recordkeeping violations.

Staff reporter Ethan Varian contributed to this story.