Last month, a mysterious gooey substance coated the feathers of hundreds of birds in the San Francisco Bay and killed more than 300.
On Friday, state and federal scientists announced they are closing in on the identity of the thick compound. And as CBS News correspondent John Blackstone reports, they have not ruled out the possibility that it was intentionally dumped into the water.
When birds started showing up covered in something oily along the eastern shore of San Francisco Bay last month, both rescuers and researchers went into action.
Nobody had seen anything quite like the substance that was sticking to feathers, making it impossible for the birds to stay warm and dry.
"This is a true mystery. What we know is it's not petroleum, which is good news. What we don't know is what it is," said Andrew Hughan, information officer at the California Fish and Wildlife Department. "It has the consistency of rubber cement like out of the jar that we did as kids."
The birds were taken for cleaning to International Bird Rescue, an organization that has saved birds at oil spills and other environmental disasters around the world. They were puzzled too.
"We don't [know what it is]," said International Bird Rescue member Barbara Callahan. "We are very much waiting to hear if the state labs have determined what the product is and, you know, once they determine the product hopefully they'll be able to find a source."
The state researchers from the Department of Fish and Wildlife were joined by others from the California Public Health Department, the Federal Environmental Protection Agency and the National Oceanic and Atmospheric Administration. Together the four agencies have determined the mystery goo is still sort of a mystery.
In a news release it's described as a "mixture of non-petroleum-based fats or oils," which may include "silicone fluids," "wood derivative oils," "animal fats and oil" and "edible and inedible seed oils."
"We're going to keep going until we can identify the material exactly or we hit a brick wall -- a wall," said California Fish and Wildlife Department member Steve Gonzalez.
Whatever it is, it still isn't known where it came from.
"We don't know if it was intentional or unintentional," Gonzalez said. "Maybe it was an accident. We don't know. If it was intentional, yes we'll pursue criminal charges."
Fortunately for the birds, the rescuers figured out how to get it off.
"We're having to soften it, if you will, with first baking soda into the feathers and then taking that off with some household vinegar," Callahan said. The recipe also includes Dawn and "toothbrushes," Callahan added. "We do use the toothbrushes just around the eyes and the mouth and the very delicate area."
More than 100 of the birds that were saved have now been released. The birds that survived are back where they belong in San Francisco Bay. The mystery goo appears to be gone.