A multi-vehicle accident closed the southbound lanes of Sonoma Mountain Parkway in Petaluma Thursday afternoon.

Police warned motorists to avoid Sonoma Mountain Parkway at Rainier Drive, and said the roadway would be closed for two to three hours as a helicopter was expected to land in the area to transport an injured occupant of one of the vehicles, according to a police alert sent at 3:30 p.m.

Motorist were advised to use North McDowell Boulevard or Maria Drive instead of Sonoma Mountain Parkway.