Several federal and state complaints against asbestos-abatement and demolition firms operating in Massachusetts have sprouted in the wake of the region’s construction boom. Involving mostly small companies and immigrant workers, the cases allege wage and benefit violations as well as improper exposure to asbestos fibers, which contain cancer-causing carcinogens.

Registered asbestos-abatement jobs climbed to more than 25,000 in 2016, a 64% increase in five years, according to Massachusetts Dept. of Environmental Protection statistics. MassDEP also conducted more than two times as many inspections in 2016 than in the previous year.

In the past two years alone, two criminal cases and three civil lawsuits were filed in the U.S. District Court in Boston. The cases were the subject of a recent WBUR public radio and New England Center for Investigative Reporting story, which said the complaints are part of a “widening U.S. Dept. of Justice activity and private civil action targeting asbestos- removal and demolition contractors for alleged worker mistreatment.”

A public affairs specialist for Boston’s federal attorney’s office, said she “cannot confirm or deny investigations” but did note that two cases concerning asbestos-removal firms are pending.

A mail-fraud and embezzlement trial involving the husband-and-wife owners of Air Quality Experts and AQE Inc.—Christopher and Kimberly Thompson of Windham, N.H.—was scheduled to begin on Jan. 30. The Thompsons allegedly defrauded the Massachusetts Laborers Benefit Fund (MLBF) of more than $2 million and entered into a union collective bargaining agreement while seeking to avoid its contractual obligations by “operating an alter ego non-union company,” according to a press release from the U.S. attorney’s office.

However, WBUR reported that, during a pre-trial hearing, U.S. District Court Judge Patti Saris said she has “deep concerns” about whether workers were defrauded. The Thompsons’ lawyer, Howard Cooper, said the case falls within a “murky” area of the law and that “Air Quality expects to be vindicated.”

In the second federal case, Ronald P. Mulcahey, a resident of Andover, Mass., will be sentenced in March. The owner of Wing Environmental Inc. in October pleaded guilty to defrauding the MLBF and the Internal Revenue Service. Mulcahey paid workers in cash to avoid employment taxes and contributions into the union benefit fund.

MLBF could not be reached for comment.

Meanwhile, 11 workers recently filed a complaint against Skinner Demolition Inc., Avon, Mass., with the Massachusetts Commission Against Discrimination, according to an agency spokesman. While the spokesman couldn’t comment on ongoing investigations, WBUR reported that Skinner underpaid the employees and failed to provide adequate asbestos protection.

Skinner Demolition owner Tom Skinner said his company subcontracts most abatement work to firms that have their own licenses and permits. He noted that, in turn, the firms “provide us with closeout documentation and disposal manifest at the end of the job.”

As for wages, Skinner said he typically reserves higher “supervisor” pay for bilingual workers. He said it is important for supervisors to be able to communicate with the client in order to “ensure safety for the employees and general public.” He has offered free English classes to workers, but they were poorly attended, he said. “It is difficult to find guys that want to lead other men and take orders from a client and be responsible for the two—and do all that within the bounds of the English language,” Skinner said.

Gary Moran, MassDEP’s deputy commissioner, noted that serious violations—that is, violations that put workers and the public at risk—are atypical. He said most asbestos contractors “know what they need to do, and they try to comply, but there are going to be contractors out there who don’t do this.”