An explosion at the Packaging Corporation of America (PCA) plant in DeRidder, La., killed three workers and reportedly injured seven on Wednesday Feb. 8. A three-person investigative team from the U.S. Chemical Safety Board (CSB) immediately deployed to the scene to investigate.

The explosion took place while contractors performed welding on a tank during a facility shutdown, according to initial reports. The explosion was powerful enough to cause the tank to fly and land in a different area of the plant.

In a statement, PCA said, "The incident involved annual repair work being performed on piping in the pulp mill area and resulted in three contractor fatalities. The cause of the incident is under investigation." The company also noted that at the time of the incident, the D1 machine was down for its annual outage. Its D3 machine was running and continues to operate.

Welding is one of several types of hot work operations that can ignite fires or explosions. Most hot work incidents result in the ignition of combustible materials or the ignition of structures or debris near the hot work.

Following a deadly 2008 explosion at the PCA plant in Wisconsin, the CSB issued a safety bulletin and video on the hazards of welding and other hot work.