(CBS) -- A malfunctioning appliance is being blamed for a carbon monoxide leak which sent 11 workers to hospitals from a Near West Side food processing plant late this morning.

The carbon monoxide leak was at Aspen Foods on Fulton Market at May Street - where they process chickens.

Chicago Fire Department Deputy District Chief Chris Lyons says one worker was taken to the hospital in fair condition; 10 others in good condition.

"I believe the CO levels were roughly 170, which is fairly high."

Workers were allowed back in less than two hours after the leak.

Peoples Gas - working with the fire department - has determined the cause to be a commercial fryer that was malfunctioning.

That fryer has now been disconnected.