PHILADELPHIA (AP) - Police are investigating gunshots fired near a south Philadelphia refinery that prompted the brief closure of a bridge spanning the Schuylkill River.

Authorities said a security guard at the Philadelphia Energy Solutions refinery reported hearing gunfire shortly before 5 a.m. Thursday.Officers responding to the scene on the westbound Passyunk Avenue Bridge found 10 shell casings from a semi-automatic weapon near the refinery entrance and on the bridge.But police found no victim or suspects, and investigators plan to check surveillance video to try to identify the vehicle involved.The westbound lanes of the bridge were closed for about an hour as officers searched for evidence but were then reopene