A powerful explosion rocked a refinery in Texas. The incident took place in Big Spring, about midway between Dallas and El Paso. Alon USA’s Big Spring refinery has been around since 1929. According to the last safety review by the Department of Labor’s Occupational Safety and Health Administration in 2002, the Big Spring refinery had no incidents, The Dallas Morning News reports.

However, Monday morning at 8:20 a.m. a blast rocked the facility with fires still burning now. It was completely shut and all flow of oil into the refinery has also been stopped. Four people were injured in the refinery explosion, a spokesman for Alon USA told CNN, but their status is unknown.

Emergency personnel closed Interstate 20 and evacuated those in the immediate vicinity of the refinery, the local Big Spring Herald reports. The publication quotes unofficial reports which state that a propylene leak in the unit sparked the explosion. The blast was allegedly heard as far as 50 miles away and shattered windows miles from the refinery.

Around 17 people work at the refinery, which processes about 70,000 barrels of crude oil a day. Fuel produced here ships to West Texas, New Mexico, Arizona, southern Oklahoma and Arkansas.

"It was extremely scary. You shook you were so scared," witness Laura McEwen told the Associated Press. "Our walls shook. It jolted your bed. It was like an earthquake."