The number of birds killed by an unknown substance in San Francisco Bay has climbed to 200, Mercury News reported.
Despite conducting tests on the mysterious goo that sticks to the birds' feathers, officials from the California Department of Fish and Wildlife still could not provide a clear explanation as to what it is.
According to the agency's laboratory personnel, the substance coats the feathers of the animals and prevents them from flying. In addition, it hinders the birds from insulating their bodies which causes them to freeze to death, Associated Press has learned.
The unknown goo, which has the same texture as dirty rubber cement, was first discovered in San Francisco on Friday of last week at Hayward Regional Shoreline, San Leandro Marina and the Harbor Bay Isle.
On Wednesday, the government department reported that the substance has affected about 315 birds in the area. These animals have been placed under the care of the International Bird Rescue Center located in Fairfield.
Authorities working with the rescue center are still on the lookout for birds that have been affected by the substance.
At first, authorities suspected that the unknown material is similar to the one that appeared in Europe in 2013. At that time, a fuel additive spilled from a ship and killed about 4,000 birds. However, tests conducted on samples taken from affected animals in San Francisco showed negative results, the SF Gate reported.
Despite the findings, the Department of Fish and Wildlife's spokesperson Andrew Hugham remained optimistic about narrowing down the actual components of the substance.
"That's really good news," he told the SF Gate. "It eliminates one possibility, but there are still lots of other things it could be."
"This is a full-bore effort," he added. "The lab has got its whole staff going. They are testing for everything."
Hughan explained that the grey-colored goo is not an organic substance like fish or vegetable oil. It is also not petroleum-based, according to lab test results.
