IMAGES FROM CHOPPER 7Slideshow: Spill Stretches From Vashon Island To Commencement Bay

An estimated 1,000 gallons of oil spilled near Tacoma from an unknown source overnight Thursday.

Ten skimmers and 11 other boats were working to clean up the oil, officials with the Coast Guard and state Ecology Department said. Crews deployed nearly 19,000 feet of boom.

Video: Oil Spreads; Wildlife Affected

A total of 238 people were involved in the cleanup effort, mostly on the south ends of Vashon and Maury islands.

Coast Guard investigators were looking for the source of the spill. They were looking at a dozen or more ships that passed through the area and were taking fuel samples for comparison.

Tacoma/Pierce County Crimestoppers, with assistance from the Port of Tacoma, was offering a $3,000 reward for information leading to an arrest and the filing of charges against the person responsible for the spill.

Anyone with information was urged to call the Crimestoppers Tip Line at (253) 591-5959.