FILE - In this Sept. 21, 2018, file photo, fire investigators pause while searching the debris at a home which exploded following a gas line failure, in Lawrence, Mass. Massachusetts lawmakers are to hold a hearing Tuesday, Dec. 11, into the safety of the state's natural gas system in the wake of September's pipeline explosions and fires in the Merrimack Valley. (AP Photo/Charles Krupa, File)
FILE - In this Sept. 21, 2018, file photo, fire investigators pause while searching the debris at a home which exploded following a gas line failure, in Lawrence, Mass. Massachusetts lawmakers are to hold a hearing Tuesday, Dec. 11, into the safety of the state's natural gas system in the wake of September's pipeline explosions and fires in the Merrimack Valley. (AP Photo/Charles Krupa, File) Credit: Charles Krupa

Natural gas companies in Massachusetts are compromising safety by increasingly turning to outside contractors for pipeline work while cutting back on staff that would oversee these projects, state lawmakers said Tuesday at a hearing following September’s natural gas explosions in the Merrimack Valley.

“There are fewer full-time employees in many of your operations than was the case five to ten years ago at a time when you’re undertaking accelerated construction activity,” state Sen. Michael Barrett, a Lexington Democrat, said to utility company executives testifying at Tuesday’s State House hearing.

“I really don’t understand how you can square fewer employees overseeing more (subcontractors) and still solemnly claim to be concerned about safety,” said Barrett, who co-chairs the Joint Committee on Telecommunications, Utilities and Energy that held the hearing.

Executives from five local utility companies pushed back, saying their staffing levels have either remained stagnant or increased in recent years.

Federal investigators have said that Columbia Gas, the utility company responsible for the Sept. 13 disaster, did not have staff on site as contractors conducted routine pipeline replacement work in Lawrence that triggered the explosions.

The National Transportation Safety Board says the company also did not have a professional engineer review the project plan before work started, a requirement that Republican Gov. Charlie Baker is now proposing to make state law.

State lawmakers Tuesday also turned a critical eye to state oversight agencies, questioning the independence of the consulting company Baker’s administration has hired to evaluate natural gas safety statewide.

Dynamic Risk Assessment Systems was picked to review the safety and integrity of the state’s aged natural gas system in the wake of the September disaster.

But on its website, the firm, which has offices in Canada and Texas, touts that its clients operate more than 40 percent of the energy pipelines in the nation.

“I’m not immediately calling into question the integrity of their work, but they seem to be part and parcel of the industry,” Barrett said. “They seem to be part of the status quo.”

Matthew Beaton, Baker’s Secretary of Energy and Environmental Affairs, said Dynamic Risk was selected because it had the required technical expertise and didn’t have any existing relationships or contracts with local utilities.

State lawmakers also took issue with the number of inspectors the state Department of Public Utilities has on staff, as well as the relatively low salaries that make it hard to retain the workers.