SAN FRANCISCO (CBS SF) — All westbound lanes of Interstate 80 on the Bay Bridge were blocked for a short time while police investigated reports of a person walking on the bridge, according to the California Highway Patrol.

A severe traffic alert was sent out at 4:50 p.m. The lanes are blocked just west of Treasure Island. All lanes were reopened at 5:03 p.m.

A man was reportedly walking along the bridge and police didn’t say whether they had taken him into custody as of 5 p.m.

Motorists are advised to expect delays and are encouraged to use alternate routes.

No other details were immediately available.