The state’s commuter rail operator is defending its handling of an incident in which a car broke free from a moving train.

The Boston Herald reported Tuesday that Keolis was criticized by Massachusetts Bay Transportation Authority officials for a lack of “critical information,” including witness statements, photographs and maintenance records in connection with the September incident.

No one was injured when an empty car detached from a commuter train on the Newburyport line. A consultant eventually blamed the accident on defective or worn out couplers that connect train cars.

The Herald said internal emails reflect dissatisfaction with Keolis’ handling of the initial investigation on the part of MBTA and federal transit officials, who considered fining the company.

A Keolis spokesman disagreed, arguing the operator provided materials in a “timely manner.”