BOSTON (AP) — Massachusetts transportation officials have ruled out equipment failure in a subway trolley accident that caused minor injuries to about three dozen people.

One MBTA Green Line trolley arriving at the Boylston Street station in Boston rear-ended another trolley stopped at the platform Thursday.

Transportation Secretary Richard Davey said Friday investigators have ruled out mechanical issues with either train or problems with tracks and signals. Davy said investigators are focusing on the actions of the moving train’s operator. He said there’s no evidence that operator was carrying a cell phone on duty.

The Boston Globe reports (http://bo.st/Ug0EVB) that the operator, who joined the MBTA in 2006, had been set to receive a safety award Friday.

Davey said the stopped trolley had its lights flashing properly, and its driver was still in the hospital as a precaution.