This post has been updated.

All lanes of the Bay Bridge have reopened following an incident in which a tanker truck began leaking propane and forced the closure of both spans.

The bridge reopened about 5 p.m., but the damage to the  evening commute was done. Cheryl Sparks, a spokeswoman for the Maryland Transportation Authority, said  the eastbound lanes opened first, shortly before 5 p.m. The westbound  lanes began moving about 15 minutes later.

At the time the lanes reopened,  however, traffic was backed up four miles in each direction, so officials were expecting lengthy delays into the evening.

The truck was westbound on U.S. 50 just before the westbound span of the bridge about 3:20 p.m. when it began leaking, said John C. Sales, a spokesman for the Maryland Transportation Authority. Crews headed to the scene to clean up the spill,.