The 7 a.m. sailing of the Spirit of British Columbia out of Swartz Bay came to an unscheduled stop in the Strait of Georgia yesterday morning when its anchor inadvertently released.

Gur Treet, a Richmond truck driver, was sleeping in his vehicle on the car deck of the Spirit of British Columbia when he was awakened by a loud banging sound at about 8 a.m.

"It was a horrible bang," Treet said in a cellphone interview from the ship. "It went on for more than 10 minutes. The ship was shuddering."

Passengers reported a large plume of what looked like dust billowing out from the rear of the ferry. The banging noise continued and the ship swayed from side to side for up to 30 minutes after the first bang, but passengers said the motion was not that noticeable.

Deborah Marshall, spokeswoman for B.C. Ferries, confirmed the vessel's anchor dropped after the Spirit of British Columbia. left Active Pass and cleared Mayne Island.

"The crew did not deploy the anchor," Marshall said. The plume of "dust" was rust particles released from the anchor's locker.

The anchor did not hook on the bottom or halt the vessel, said Marshall. Crew members brought the ship to a stop when they realized the malfunction, and started retracting the anchor before it could connect with the ocean floor.

The incident delayed the ferry by 80 minutes. Marshall said the ship would be inspected to determine the source of the malfunction.

The Spirit of British Columbia, which was built in 1993, had 509 passengers and 267 vehicles on board at the time of the incident.

jhatherly@tc.canwest.com