California Highway Patrol and Los Angeles County Fire Department officials responded to a fatal multi-vehicle crash in Calabasas Monday night.

Calls about the crash on the 101 Freeway near Las Virgenes Road came in around 9:12 p.m., Los Angeles County Fire Department officials told KTLA.

Authorities confirmed that one person died and two others had to be rescued from their vehicle.

While it’s unclear exactly what caused the collision and how many cars were involved, two vehicles flipped over and landed on opposite sides of the freeway.

Aerial images from Sky5 showed slow traffic backing up in both directions.

A an alert was issued for lanes 1 and 2 westbound and lanes 1, 2 and 3 on the east side of the freeway which is expected to last at least two hours.

CHP is investigating the cause of the accident.