A report of a human finger found in a bowl of chilli at a branch of fast food chain Wendy's have hit the company's sales in the San Francisco area, according to a  company spokesman quoted by the Reuters news agency.

"We've had a severe sales impact from this, particularly in the San Francisco-San Jose bay area," said spokesman Bob Bertini from Wendy's corporate headquarters in Dublin, Ohio.

"It's very important to us to find out what happened in this incident. We believe someone knows exactly how the piece of finger got into the chilli bowl," he said.

The company has offered a $50,000 reward to the first person offering verifiable information about how the finger found its way into a bowl of chilli at a franchise in San Jose, California, on March 22.

The San Francisco Chronicle reported this week that police has searched the home of Anna Ayala of Las Vegas, who filed a complaint about biting into a human finger after spooning up a mouthful of chili at the San Jose Wendy's on March 22.

A San Jose Police Department sergeant would say on Saturday only that investigators traveled to Las Vegas this week to serve a search warrant in a private home connected to the case. "The investigation continues," added Sgt. Nick Muyo, declining to further describe the search.

Wendy's has said its own investigation found no evidence of any finger or hand accidents among workers or suppliers at the San Jose franchise in late March.