A Green Line derailment that injured 10 people on Monday was caused by human error, the MBTA said Friday. A source also said the trolley driver has been fired."The motorperson failed to operate his trolley in compliance with speed and signal requirements," the MBTA said in a statement. "The MBTA's investigation had previously ruled out any problems with the trolley, tracks, switch or signals."A source tells NewsCenter 5 that the trolley operator, Sydley Gardner, has been fired. The day after the crash, the MBTA said speed was a "contributing factor" in the crash.Gardner, 48, who has worked for the T for five years, was initially placed on paid leave pending an investigation.Service on the Green Line resumed Tuesday after the trolley jumped the tracks, injuring 10 people, including two MBTA employees. None of the injuries were serious.A second train slammed on the brakes to avoid hitting the first train and tossed passengers around.Gardner was fired in September 2010 after his Green Line trolley hit a pedestrian. Gardner was not found at fault, but was fired for not following protocol after the incident. He was reinstated by an arbitrator due to a technicality, sources told NewsCenter 5.

A Green Line derailment that injured 10 people on Monday was caused by human error, the MBTA said Friday. A source also said the trolley driver has been fired.

"The motorperson failed to operate his trolley in compliance with speed and signal requirements," the MBTA said in a statement. "The MBTA's investigation had previously ruled out any problems with the trolley, tracks, switch or signals."

A source tells NewsCenter 5 that the trolley operator, Sydley Gardner, has been fired.

The day after the crash, the MBTA said speed was a "contributing factor" in the crash.

Gardner, 48, who has worked for the T for five years, was initially placed on paid leave pending an investigation.

Service on the Green Line resumed Tuesday after the trolley jumped the tracks, injuring 10 people, including two MBTA employees. None of the injuries were serious.

A second train slammed on the brakes to avoid hitting the first train and tossed passengers around.

Gardner was fired in September 2010 after his Green Line trolley hit a pedestrian. Gardner was not found at fault, but was fired for not following protocol after the incident. He was reinstated by an arbitrator due to a technicality, sources told NewsCenter 5.