Four former MBTA inspectors and one current T supervisor pleaded not guilty Thursday to federal charges that they falsified Red Line track inspection records while using an agency garage as their own “automobile repair shop.”

Prosecutors alleged the quintet of employees submitted or greenlit reports last fall describing track inspection work, despite surveillance video showing them engaged in conversation, using cellphones or working on motor vehicles at the same times that the inspections supposedly took place.

Prosecutors charged 62-year-old Ronald Gamble of Dorchester, 42-year-old Jensen Vatel of Brockton, 53-year-old Nathalie Mendes of New Bedford, 36-year-old Andy Vicente of Bridgewater and 47-year-old Brian Pfaffinger of Marshfield with falsification of records and making false statements.

All five pleaded not guilty, according to U.S. Attorney Leah Foley’s office.

“The charges are a federal overreach into an internal personnel matter which should be handled by the MBTA, not the court system,” said Michael Tumposky, an attorney for Gamble. “Mr. Gamble looks forward to exonerating himself at the conclusion of this process.”

Attorneys for the other four defendants did not immediately respond to requests for comment.

Prosecutors alleged in the 25-page indictment that the quintet and other unnamed Red Line employees “treated and operated the Cabot Garage as an automobile repair shop during MBTA work hours.”

The falsification of reports allegedly took place between at least Sept. 3 and Oct. 15, 2024 while the MBTA was approaching the end of a year-long repair campaign designed to eliminate subway speed restrictions required by federal regulators due to concerns about the state of MBTA infrastructure.

Prosecutors alleged that each of the four inspectors in that span filed a report claiming to have examined Red Line tracks. But during the timeframes they claimed to be out on the system, surveillance cameras recorded Vicente working on non-MBTA vehicles, Mendes sitting inside her car, Vatel chatting with other employees outside the Cabot Yard garage, and Gamble inside the garage moving private vehicles.

In one case, the indictment alleged, “Gamble claimed to have verified four separate defects, on different tracks, within one minute,” in the final minute before his inspection ended.

Pfaffinger, who according to prosecutors still works at the T, allegedly submitted a false work order for a falsified inspection report filed by Gamble covering a period of time when the two were together inside the garage.

Foley’s office said Pfaffinger “allegedly not only knew that his subordinates worked on private vehicles during work hours, but had his subordinates work on his own vehicle.”

WCVB reported in October that employees at Cabot Yard were on leave amid an investigation into whether they worked on personal vehicles while on the job. By December, a total of eight employees had been terminated in connection to the probe, according to WCVB.

Gamble, Vatel, Mendes and Vicente no longer work at the MBTA, according to the indictment, which describes them as “former” employees. The indictment calls Pfaffinger a current employee and “previously a supervisor.”

MBTA Transit Police referred the matter to the U.S. attorney’s office last year, the T said.

“The MBTA thanks the U.S. Attorney’s office for their thorough investigation and diligent work toward holding people accountable for alleged criminal activity. As a public agency, it is our responsibility to be good stewards of public resources and deliver safe and reliable service to transit users. That’s why General Manager Phil Eng took immediate action to hold these employees accountable when this misconduct came to light,” MBTA spokesperson Joe Pesaturo said in a statement. “Their actions do not reflect the values of the MBTA, and they will not impact the improvements we continue to make across the system. We are taking these allegations very seriously, as we have an obligation to the public and to our workforce to ensure that every employee meets the highest standards of conduct.”

All five defendants face charges of making false statements and falsifying records.

Inspections typically take place using MBTA-issued cellphones and an app called MaxTrax, according to the indictment. An inspector opens the app and walks the relevant length of track, recording any issues they observe, then confirms the process is complete by touching a finger to the phone and signing their name.

The MBTA is overseen by the state Department of Public Utilities and by the Federal Transit Administration.

The T conducted a major track overhaul campaign last year after a series of problems thrust infrastructure woes into the spotlight. Officials announced in November that successful repairs allowed the Red Line to run end-to-end without speed restrictions for the first time in at least 20 years.

Also on Thursday, former MBTA Transit Police Sgt. David Finnerty was convicted of aiding and abetting the filing of a false report. Finnerty had been charged for helping to cover up the physical assault of a man by Transit Police Officer Dorston Bartlett.

“Finnerty helped Bartlett draft a false arrest report regarding the incident, with the intent to impede any federal investigation of Bartlett’s unconstitutional use of force,” Foley’s office wrote.