PHILADELPHIA (CBS) — Authorities are investigating an oil spill in the Schuylkill River.

Officials responded to a call shortly before 5:00 p.m. on Monday afternoon. Crews were on the scene on the 2400 block of Chestnut Street.

At this point, it is not clear how much oil spilled into the river. The cause of the spill is also not known at this time.

Officials say the oil is covering half of the river. The spill is from Chestnut Street to South Street.