(Reuters) - Intruders beat to death more than 900 chickens, some of them with a golf club, during a break-in at a commercial poultry farm in central California, authorities said.

The Fresno County Sheriff's Office said the suspects pulled back part of the fence to enter the Foster Farms facility.

"Once inside, the suspects used a golf club, and possibly another similar type instrument, to slaughter the birds," it said in a statement, adding that 920 chickens were killed.

Livingston, California-based Foster Farms said it was "an unconscionable act of animal cruelty" that appears to be a random act of violence.

"Foster Farms is working with local law enforcement ... and is offering a $5,000 reward for information leading to the arrest and prosecution of the persons responsible," it said in a statement.

The incident happened on Sept. 20 but only came to light on Tuesday after the sheriff's office called for the public's help in identifying those behind the crime.

(Reporting by Daniel Wallis in Denver)