Custodial and maintenance workers at Oakland International Airport and at one of the nation's busiest seaports returned to work late Tuesday, ending a one-day strike that had shut down the Port of Oakland.

There were long lines of trucks early Wednesday entering the sprawling facility as the busy seaport tried to load up cargo that had backed up during the 24-hour shut down.

The port handles roughly about 2.3 million cargo containers a year, generating about $300 million in revenue. Officials, however, say the facility is $1.3 billion in debt.

The 24-hour protest was over stalled contract talks between port officials and the Service Employees International Union Local 1021.

Union officials didn't immediately return calls late Tuesday, but a message posted on the union's website by SEIU Local 1021 President Roxanne Sanchez said both sides would be returning immediately to the bargaining table.

During the strike, workers outside the port blocked trucks from picking up and delivering goods on what had been expected to be a busy day before the holidays.

Port of Oakland spokesman Isaac Kos-Read said "numerous" trucks were stopped from entering the port and that there were "major issues in terms of blockages." He declined to elaborate.

Dozens of truck drivers decided not to interrupt the protest.

"What can you do?" David Soria, a driver for Modesto-based Rocha Transportation, said as he waited to drop off a shipment of wine. "My company told me to stay, so I'll stay. And wait."

Kos-Read said it was unfortunate that truckers were forced to stop work and wait in the rain.

On Tuesday, ships waited at six of the seven terminals at the Port of Oakland, as intermittent rain soaked hundreds of angry workers who carried signs and blocked entrances during the protest.

Passing motorists blared horns and supporters pounded drums as strikers chanted, "Shut it down. We're a union town!"

"We're letting management and the public know that they can't treat us like that," Lynn Riordan, a communications staffer for the union, said earlier Tuesday.

Across town, dozens of additional service union members picketed at Oakland International Airport after walking off their jobs late Monday. Those employees are covered under the same contract as port workers.

No flights were affected, Kos-Read said.

By midday, union officials said that Oakland Mayor Jean Quan had stepped in to bring the parties back to table to continue contract talks.

The port declared an impasse in negotiations in May, and the two sides are still scheduled to meet later this month. The talks broke down amid issues involving pay, benefits and a demand by the port that custodial and maintenance workers contribute to their retirement fund.

The service union, which represents electricians, clerical workers, security personnel and janitors, claimed the port is withholding requested financial information. The union also said port officials have implemented unilateral changes during bargaining sessions.

"We're showing you that if you don't take us seriously, we have the ability to shut down the port," said Gary Jimenez, a union vice president.

The protest marked the latest work stoppage at the port within the past 12 months. Occupy Oakland demonstrators shut it down twice last year.