Four former MBTA employees who clocked in overtime well north of $50,000 last year and a current staffer could face up to 20 years in prison for allegedly falsifying Red Line track inspection reports.

The four former employees are accused in federal court of working on private vehicles, playing on their phones, and chatting with other employees instead of performing track inspections, which they stated they completed.

The current lone staffer, who is on leave after being disciplined, had supervised the fired employees and allegedly had his subordinates work on his personal vehicle, according to charging documents.

Authorities arrested Brian Pfaffinger, 47, of Marshfield; Ronald Gamble, 62, of Dorchester; Jensen Vatel, 42, of Brockton; Nathalie Mendes, 53, of New Bedford; and Andy Vicente, 36, of Bridgewater, on Thursday morning following their indictments.

All five face charges of falsification of records, aiding and abetting, and false statements, aiding and abetting, in connection with their alleged activity, which prosecutors say took place at Cabot Yard in South Boston between Sept. 3, 2024, and Oct. 15, 2024.

In a statement, the MBTA thanked the Massachusetts U.S. Attorney’s Office for its “thorough investigation and diligent work toward holding people accountable for alleged criminal activity.”

“As a public agency,” it added, “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.”

Agency officials had let go of a total of eight employees as of last December, MBTA spokesman Joe Pesaturo told the Herald at the time. Last October, the agency started probing suspected criminal activity at the Cabot Yard maintenance facility, where Red Line vehicles are stored, and track workers and inspectors are based.

Charging documents outline the alleged misdoings, with video surveillance showing Vicente sitting inside Cabot Garage holding a cellphone; Mendes sitting inside her vehicle, and allegedly not leaving until after the inspection; Vatel chatting with other MBTA employees; and Gambel performing detail work on a private vehicle.

In a separate incident, on Oct. 14, Gamble is accused of creating an “inspection report alleging he conducted an inspection; however, according to surveillance video, Gamble was inside of Cabot Garage with Pfaffinger.”

“Despite knowing that the inspection report was false, and that Gamble was at Cabot Garage on Oct. 14, 2024, the following day, Pfaffinger allegedly created supporting documentation for Gamble’s Oct. 14, 2024, inspection, which he knew to be false,” a release from the U.S. Attorney’s Office states.

Falsification of records and aiding and abetting the falsification of records provides a sentence of up to 20 years in prison to be followed by up to three years of supervised release and a fine of up to $250,000.

Charges of false statements and aiding and abetting false statements carry a sentence of up to five years in prison, up to three years of supervised release and a fine of up to $250,000.

Mendes, Vicente, Vatel and Gamble all raked in more than $50,000 in overtime last year, shooting their total pay north of $150,000, charging documents show. Gamble led the pack with $121,476.51 in OT and $241,014.67 in total compensation.

Pfaffinger, who earned $144,009.82 in total pay last year, could face further disciplinary action, including termination, the MBTA said Thursday.

“Their actions do not reflect the values of the MBTA, and they will not impact the improvements we continue to make across the system,” the agency said of the employees. “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.”