PERKIOMEN TWP., Pa. -

State Police are still investigating what caused a crash Monday night in Montgomery County.

Officials say the two-car accident happened sometime after 9 p.m. on Township Line Road on the border of Limerick and Perkiomen townships.

The driver of one car -- a woman -- was airlifted to a nearby hospital in serious condition.

The other driver -- a man -- also suffered unknown injuries.