Police are investigating after an elderly woman riding an Edmonton Transit bus was injured and suffered a medical episode after the bus was involved in a collision.

Police say a Chevrolet Impala was trying to cross Terrace Road near 57th Street just after 1:30 p.m. Saturday when it collided with the bus.

Neither the bus driver nor 78-year-old female driver of the car sustained any life-threatening injuries. 

The 87-year-old passenger was hurt in the collision, however, and police say she had a medical episode at the same time.

The woman was treated by paramedics and then rushed to hospital where she remains in serious condition.

A second woman, 71, who was also a passenger on the bus was taken to hospital after the crash but later released.

No charges have been laid yet but police say the collision is still under investigation.