WASHINGTON (Reuters) - The U.S. National Transportation Safety Board (NTSB) said Thursday it will investigate the collision of two trolleys in Philadelphia that injured 46 people and sent 25 to the hospital.

NTSB said it will send a team to Philadelphia to look at collision avoidance and federal oversight issues after one trolley rear-ended another Wednesday. The Southeastern Pennsylvania Transportation Authority said Wednesday that none of the injuries were life threatening.

(Reporting by David Shepardson)