PHILADELPHIA (CBS)—Authorities are investigating what led to the alleged assault of a SEPTA bus driver on Monday morning.

SEPTA officials tell CBS 3 that while a bus was stopped at the intersection of Rising Sun Ave. and Adams Ave. two men boarded and threw an unknown liquid on the woman driving the bus.

She was transported to an area hospital to be evaluated. Her condition is unknown at this time.

No further information is available at this time.