BUTLER TWP — No one was injured Tuesday evening when a storage tank caught fire at a natural gas well site on Meridian Road.

The cause of the fire at the Rex Energy gas well pad was not immediately determined, authorities said.

But company officials revealed that preliminary information indicated a valve on one of the tanks malfunctioned.

No natural gas condensate was released from the holding tank. The liquid condensate, which contains hydrocarbons, is a byproduct of natural gas extraction.

“At about 6:45 p.m. (Tuesday), a small fire occurred on a production tank at our Lynn well pad in Butler Township,” Mike Endler, Rex Energy's senior director of civil and environmental engineering, said in a statement.

He said two wells at the operation were immediately shut down.

The fire burned for less than an hour before Butler Township Fire District 3 firefighters got there and quickly put out the blaze with a chemical extinguisher.

“We blanketed the fire with a dry chemical agent,” said District 3 Chief Toby Wehr. “In 30 or 40 seconds, it was out.”

A drilling crew for Mark West Energy Partners spotted the fire about 6:35 p.m. and called 911. The crew was about 1,000 feet away working on a hillside above the gas well pad in the 600 block of Meridian Road near Powder Mill Road.

“It was going pretty good,” said one worker who requested anonymity. “It's something I never expected to see.”

The storage tank on fire was one of six at the well head. Four of the tanks contained produced water, which is water released from the earth during the drilling process, and two contained condensate.

Each tank stores about 300 barrels of either water or condensate removed during the gas extraction process, authorities said. One barrel equals about 42 gallons of water or condensate. It was not clear how much liquid was in the tanks.

The flammable liquid placard on the tank that was on fire showed it was “very flammable,” Wehr said.

But no evacuations were necessary, said Steve Bicehouse, county emergency services director.

Wehr said once firefighters got to the site, they used a cat walk between the tanks to get in position to fight the fire.

“At that time, it was small,” he said of the blaze.

He said firefighters have received extensive training in gas well emergencies and were prepared to get the job done.

Assisting Fire District 3 were firefighters from Penn Township, Evans City, Connoquenessing and Saxonburg. The county's Hazardous Materials Team also responded.

Additionally, the state Department of Environmental Protection was notified. A DEP official was at the scene but was unavailable for comment Tuesday night.

Rex Energy and the DEP continue to investigate the fire.

Endler said the company would “take all necessary steps to determine” what caused the fire.

“We do not believe that any environmental or health impacts occurred as a result of this event,” he said. “We thank the first-responders for their professionalism and efforts.”