West Coast seaports were back at full operation Sunday, except in Oakland, California, which has seen another work disruption.

It's unclear what prompted the problems in Oakland. Work at the other 28 West Coast ports is back to normal, Pacific Maritime Association spokesman Steve Getzug said.

Work at all the ports had slowed significantly over a months-long contract dispute, causing huge backups. A tentative deal was struck late Friday, and by Saturday night workers in Oakland and the other ports from San Diego to Seattle were starting to clear the backlog.

West Coast seaports handle roughly one-quarter of U.S. international trade, an amount worth about $1 trillion annually.

Dockworkers in Los Angeles worked an overnight shift for the first time in weeks Saturday night, port spokesman Phillip Sanfield said.

It will take several months for ports such as Los Angeles and Long Beach — the nation's largest — to clear the backlog, which swelled as the two sides quarreled over a new deal.

"There's a lot of work to do and a limited labor pool. But it's being distributed between the two ports and the cargo containers between both LA and Long Beach as equitably as possible," Sanfield said.