PORT OF OAKLAND, Calif. (KGO) -- The International Bird Rescue released 20 healthy seabirds endangered by mysterious goo back into the wild on Wednesday.
The birds released at the Port of Oakland are part of a flock of 330 rescued by the organization since January.
The mysterious substance killed more than 150 with 132 still receiving treatment.
Investigators haven't identified the mystery goo that jeopardized the birds.
There haven't been any new cases in nearly two weeks.
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.