AN INTERNAL MBTA DOCUMENT indicates a probe of parking fee losses now extends to more than one station and refers to a terminated employee who had been working for the private parking lot operator.

CommonWealth first reported on the parking fee discrepancies on April 6. At the time, T officials issued a statement saying discrepancies had been found only at the North Quincy station on the Red Line. The officials indicated they had asked the private parking lot operator, LAZ Parking, for a full accounting.

Five days later, on April 11, the T said its transit police had taken over the probe. T officials declined to provide any additional information on LAZ’s response to inquiries or the size of potential parking revenue losses.

A source close to the investigation said the T called in its transit police and auditors because the report from LAZ Parking was inadequate. The LAZ report apparently uncovered “doctored reports” at the North Quincy station and indicated a supervisor there had failed to follow proper procedures and “was likely responsible for shortages.”

But the LAZ report did not document losses at North Quincy or fully explore potential losses and significant shortages in fees at parking lots at the Lechmere and Riverside T stops. T officials also said a LAZ employee had been terminated at the Lechmere parking facility, apparently in connection with the parking probe.

A letter dated April 14 from Ronald Ross, the T’s director of parking, to Marc Lutwack, the executive vice president at LAZ Parking, cited numerous deficiencies in the LAZ report and said the T transit police were being called in to conduct “a thorough, comprehensive review.”