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Some of the dead western gulls that washed ashore on Huntington Beach last month tested positive for a type of botulism more commonly associated with humans.

That was the unexpected finding from necropsies performed on the birds, the Wetlands and Wildlife Care Center said Friday.

On Oct. 10, personnel from the care center responded to a report of numerous dead or dying sea gulls on Huntington State Beach, which is across from the nonprofit organization’s facility.

With the help of a lifeguard, they rescued four gulls that were found tangled in seaweed at the high tide line, according to a news release from the care center.

Eight other beached seabirds found at the site were already dead.

The live sea gulls were all clinging to life and suffered from generalized paresis so severe that they couldn’t even close their eyes; one ended up dying, according to the release.

Two of the remaining gulls were released this week, while a third remains in the organization’s care.

Necropsies performed at UC Davis on two of the birds found that they had enlarged hearts and livers, a sign of acute toxicity.

Five other gulls were sent to the California Department of Fish and Wildlife’s investigative laboratory, which found the toxicity was from botulism type A, according to the release. The results were released Friday.

Type A is more common in humans, with improperly canned foods among the most common sources.

In humans, the serious and potentially deadly illness can cause difficulty breathing and muscle paralysis, according to the U.S. Centers for Disease Control and Prevention.

The most common form of botulism found in birds is type C, with the occasional type E diagnosis among those that eat fish.

The source of the seabirds’ illnesses is unknown, but five more exhibiting the same symptoms were recovered in the area within the past few weeks, officials said.

Two have died, but three are still being treated at the Wetlands and Wildlife Care Center.

An investigation is underway to determine a source of the botulism.

Anyone who sees a sick or weak seabird in Orange County is asked to contact the care center by calling 714-374-5587.