DERIDDER, Louisiana (From local news reports) -- Three people are dead, one is missing and several have been injured following a paper mill explosion Wednesday at a Louisiana containerboard mill.

The explosion occurred at the Packaging Corporation of America's DeRidder Containerboard Mill at about 11:10 a.m. CST according to the Beauregard Parish Sheriff's Office. It is being reported that two tanks at the containerboard mill exploded, killing three people and injuring many more, according to officials. It was later reported that the explosion was from a rupture at the secondary process tank in the pulp mill area and the mill could be back up in two to three weeks.

Calls to the mill by Paperitalo Publications have not been returned.

The scene has been contained and multiple police, fire and first responders are at the facility which is on U.S. 190 between Deridder and Merryville, La. Ambulances are on the scene and Louisiana State Police is sending a hazardous materials team to the facility.

The facility produces about 874,000 tons of containerboard each year, according to the company, which acquired the mill from packaging company Boise in 2013. The company, in total, also reports producing more than 3.7 million tons of kraft linerboard annually.

***UPDATE 1: Three people are dead following an explosion at Packaging Corporation of America, Beauregard officials have confirmed.

One person was unaccounted for, but has been found and is safe, said Sgt. James Anderson, state police Troop D spokesman.

Anderson said seven people were injured in the explosion -- one with moderate injuries and six with minor.

Victims were transported from the location by ambulance and by helicopter.

Beauregard Memorial Hospital received three patients, according to Kelli Brooks, director of public relations. All are in stable condition and one has been discharged.

***UPDATE 2: All three men who died were contractors who were working in the pulp mill area, according to a statement released by PCA:

"At approximately 11:10 am CST, Wednesday, February 8th, there was an explosion at our DeRidder, LA paper mill. 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.

"Our primary concern is for the safety and well-being of the people working on our site. The top priorities at this time are the notification of families of the deceased contractors and investigation of the incident with authorities.

"At the time of the incident, the D1 machine was down for its annual outage and the D3 machine was running and continues to operate. The current assessment indicates that the annual outage work is expected to be delayed by up to one week and the mill will then resume full operation. Further information will be provided, as appropriate, when it becomes available."

Welding activity was taking place in the vicinity of the tank that exploded, said Sgt. James Anderson, state police Troop D spokesman. The tank contained "foul condensate, which is a by-product of the cooking process." Authorities are still investigating to see what other chemicals were in the tank.

Anderson called the blast a "strong explosion."

*****

Join Jim Thompson on the 2nd Annual Papermakers Mission Trip to Guatemala, 22 - 29 July 17. Build houses, talk about the pulp and paper industry. For more information, email jthompson@taii.com with "Guatemala" in the subject line.