Police in California stumbled across a trash-strewn industrial building crammed with more than 1,000 snakes, parrots, chickens and other animals — many of them dead — when they arrived to serve an arrest warrant on a man who rented the property.

The surviving animals were being examined and sheltered on Friday by the Inland Valley Humane Society and SPCA.

"Almost 2,000 chickens, parakeets, lovebirds, and other exotic birds were rescued from an industrial warehouse this morning … dozens of exotic fish were found at the location," the Inland Valley Humane Society and Society for the Prevention of Cruelty to Animals said in a statement.

Police originally arrived at the industrial building in Montclair, 48 kilometres east of Los Angeles, to make an arrest unrelated to the animals. They had asked humane society workers to accompany them to care for the man's two dogs while he was in custody.

But when they got there, humane society operations manager James Edward said on Friday, they immediately became suspicious that other animals were inside.

A search warrant was served and authorities entered to find more than a thousand chickens, baby chicks, parakeets, parrots, love birds, snakes and fish.

"Unfortunately there were numerous deceased chickens and snakes," Mr Edward said, adding conditions were deplorable.

"It's the worst I've seen in nine years in the association," Silvia Lemos, a member of the Humane Society told ABC.

Trash and debris were strewn everywhere, he said, and fish were swimming in tanks so filthy it was impossible to identify them. Snakes were locked in boxes without food or water. The building, itself, reeked of ammonia.

"It was definitely uninhabitable for animals or people," Mr Edward said.

Police did not immediately release the arrested man's name, and Mr Edward said authorities did not know why the animals were kept there.