Customers and employees at the United States Post Office in Stephenville received a surprise Wednesday morning when they had to evacuate the building.

Employees reported a strong odor of natural gas in the building and called 911 while Postmaster Lisa Montfort had employees and customers evacuate as a precaution.

A prompt response by Stephenville Fire Department resulted in a search of the building and the location of the odor.

“They have new heaters and we think it was stuff burning off those new heaters,” Stephenville Fire Chief Jimmy Chew said.

Captain Randy Spikes said new heating and air conditioning units were installed on top of the building earlier this summer, but due to the high temperatures a “burn-in” was not completed on the heating portion of the units.

“Apparently it got cold enough last night that they came on, (creating the odor),” Spikes said.

The fire department entered the building, searching for carbon monoxide and other combustible gases. Firefighters did not find anything, but kept the building clear until Atmos Energy arrived and completed a thorough search for a gas leak.