COOS BAY, Oregon (CNN) -- Oyster growers are furious about a decision to burn the grounded cargo ship New Carissa, and fear that oil flowing toward tidal flats could threaten $10 million worth of shellfish.

The 639-foot Japanese-owned cargo ship ran aground on the beach a mile north of the entrance to Coos Bay on February 4 and last Monday began leaking oil from its fuel tanks.

Worried that the ship would break apart in stormy weather and spill nearly 400,000 gallons of tarlike bunker fuel oil on southern Oregon beaches, authorities came up with a bold plan to crack open the ship's fuel tanks with explosives and set the fuel on fire with napalm.

With a fiery explosion Thursday night, the fuel was ignited and during the blaze the ship cracked apart, spilling more oil. Authorities have estimated at least two-thirds of the fuel has burned.

"This is prime oyster growing ground," said Lilli Clausen, who with her husband, Max, has been growing oysters in Coos Bay since 1980 to ship around the world. "Whoever made the oil spill response didn't consider oysters."

The spill came at a critical time for oyster farmers: just as they were preparing to set out new oysters for the next generation. Clausen lets her oysters grow three years before harvesting them.

Tarballs and a light sheen of oil from the ship have flowed about five miles into Coos Bay, prompting the state's agriculture department on Friday to shut down harvests at the four oyster farms there. So far, 25 dead birds have been found, 11 of them oiled.

Officials will test to see if shellfish have been contaminated.

The ship fire, which was briefly reignited Saturday after burning out overnight, was out again Saturday afternoon.

Less than 10 percent of the fuel is believed to have leaked out since cracks developed in the fuel tanks Monday.

"My opinion is that with the light amount of oil coming in they will survive," said John Johnson, shellfish biologist with the Oregon Department of Fish and Wildlife.

Recreational shellfishing has been banned in the area and crab fishermen have been unable to pull pots in an area around the grounded ship closed to the public.

"We just don't want to take any risk of oiled shellfish getting out to the public," said Deb Cannon of the Oregon Department of Agriculture.

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