FAIRFIELD (CBS SF) — The International Bird Rescue will release its first batch of cleaned seabirds recuperating from getting covered in a mysterious goo on the shores of the East Bay and the Peninsula, bird rescue officials said Tuesday.

The bird rescue nonprofit plans to release 15 to 30 seabirds at Fort Baker in Sausalito on Wednesday, where there is plenty of food with a large herring spawn going on and tens of thousands of other seabirds of the same species feeding there.

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Most of the 323 birds brought to the International Bird Rescue facility in Fairfield are surf scoters, horned grebes, scaups and common goldeneyes. There are still 221 recovering there, but 102 died after they were brought in covered with the mysterious sticky substance.

At least 150 more also died from exposure to the substance.

Bird rescue executive director Barbara Callahan said she talked to state investigators Tuesday afternoon and they are no closer to identifying what the substance was or where it came from, but is not believed to be petroleum-based.

Regardless, it appears to be gone and there have been no reports of birds covered with the gunk since Thursday.

Birds first started showing up covered in the substance on Jan. 16 on the bay shores in the East Bay including Alameda, Oakland, San Leandro, Hayward and Fremont. Some birds also were found on the Peninsula.

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The affected birds had to be thoroughly washed and dried, which disrupted their feathers’ ability to waterproof themselves and protect the birds from exposure to the cold bay waters.

Once cleaned at the International Bird Rescue facility in Fairfield, they are moved to pools there to finish recovering. When their ability to waterproof has been restored and they are not suffering any other medical problems, they can be released, Callahan said.

“Everybody’s been cleaned and is in various stages of waterproofing at this point,” she said Tuesday afternoon.

The rest of the birds are expected to be released over the next 10 days, Callahan said. Rescuers have not decided where they will release the remaining birds, but in addition to Sausalito they have used Crissy Field in San Francisco and locations in the East Bay in the past.

“If they choose to go back to the East Bay at least that’s clean over there now,” Callahan said.

Since the source of the substance hasn’t been identified, the bird rescue has had to foot the bill of helping the cleaning and recovery of the birds they’re taking in at a cost of $9,500 per day. The bird rescue has been requesting donations, which can be made via their website at http://www.bird-rescue.org.

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