Four employees at a Bronx air conditioning repair store were taken to the hospital on Friday after being exposed to carbon monoxide fumes.

The store?s manager was initially alerted to the leak when one of his workers became sick. Four people were taken to Lincoln Hospital while two others were treated in emergency vehicles, officials say.

In total, 25 people were evacuated. The source of the fumes was later determined to be three gas-fired heaters. Employees were allowed to go back to work an hour after the fire department investigated the problem.

The air conditioning repair store and several other offices occupy the building on Walton Avenue.

Con Edison has temporarily shut down the heaters since the evacuation.