EDMONDS — Normal ferry service resumed Monday afternoon between Edmonds and Kingston, after a diesel spill halted most sailings that morning.

Ferry officials said service returned early enough to avoid longer-than-normal backups at the end of the busy Labor Day holiday.

“Typically, the return traffic on the weekends will grow as the afternoon progresses,” state ferries spokeswoman Marta Coursey said.

Ferry workers noticed problems before the day’s first departure out of Kingston at 4:55 a.m. Monday, Coursey said.

They stopped both boats on the run, the Walla Walla and the Spokane, which were in Kingston. They called in the U.S. Coast Guard and an oil-response contractor.

The Spokane was cleared to leave Kingston at 10:25 a.m., Coursey said.

The Walla Walla, where the spill occurred, was cleared to leave at 12:50 p.m., following cleanup.

Throughout the early morning, the ferry system directed holiday travelers to take the Seattle-Bainbridge or Seattle-Bremerton ferries instead. The Edmonds-Kingston route is the third-busiest in the system and carried nearly 3.9 million passengers last year.

The Coast Guard monitored Monday’s cleanup effort performed by a contractor for the state. Crews used containment booms around the ferries to prevent the fuel from spreading.

“We received a report at approximately 4:30 a.m. from the ferry service that the ferry Walla Walla had suffered an equipment failure as they were transferring diesel fuel between tanks on board,” Petty Officer 3rd class Katelyn Shearer said. “The estimate was that approximately 15 to 20 gallons of diesel spilled onto the deck of the ferry and that about 10 gallons had spilled into the water.”

Coast Guard officials deemed the cleanup complete at 11:30 a.m., Shearer said.

In the Edmonds ferry line, motorists took the delay in stride. Backups were short as people waited just after 10 a.m.

“There was no traffic when we showed up,” said Glenn Winkey, 62, a retiree from Spokane who had been waiting about an hour. “I didn’t expect to be first in line.”

This report uses material from The Associated Press.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com. Twitter: @NWhaglund.