MARIN COUNTY (CBS SF/BCN) — The instability of a boat grounded since early Saturday on a rocky coastline near Dillon Beach in Marin County is hampering an investigation into whether any fuel spilled from the 90-foot vessel, the American Challenger.

A tugboat was towing the 90-foot American Challenger from Puget Sound, Washington, when a rope got tangled in the tug’s propeller Friday morning, setting the boat adrift.

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Coast Guard Cutter Hawksbill responded to the scene, but the crew was unable to board the drifting boat to attach a tow line due to weather conditions, the proximity to shore and the unknown structural integrity of the unmanned vessel, according to a statement released Tuesday by the unified command of local, state and federal officials responding to the incident.

Californian Fish and Wildlife observe Dillon Beach (CDFW – Office of Spill Prevention and Response)

The American Challenger eventually came aground at 1 a.m. Saturday north of Dillon Beach.

Due to the instability of the vessel — and the risk to the safety of surveyors — officials with the unified command said efforts to obtain an accurate reading of the amount of fuel aboard the boat will take time.

Environmental assessments are continuing on shore but have not found additional evidence of a spill, following reports of some sheen in the immediate vicinity of the vessel and along the shoreline adjacent to the vessel.

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Brown foam has been washing up on Dillon Beach, but investigators said the foam is normal biological material. Also, crews on shore have yet to find any oiled wildlife or damage to wildlife habitat.

Crews set up 4,000 feet of boom around the boat to protect marine wildlife like the oysters in Tomales Bay. A 100-foot gap exists in the boom to give recreational boaters access to the deepest point of the channel south and east of Hog Island.

If the oyster beds become threatened, the gap will be closed, according to the unified command.

All the beaches in the area are open, but Miller Boat Launch is closed temporarily to help with the emergency response efforts. The efforts to clean up the sheen is not affecting commercial boat traffic.

If any oiled wildlife is seen, the public was asked to avoid approaching the animal and instead call the Oiled Wildlife Care Network at (877) 823-6926.

For more updates on the investigation and cleaning, visit calspillwatch.wordpress.com.

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