Seven employees have been injured after an explosion at the Georgia-Pacific plant in Corrigan.

The small town with 1,600 residents is located about 90 miles north of Houston. According to officials, the incident happened about 6:30pm Saturday along Industrial Road, near a major highway.

The fire was so intense it took two hours to extinguish the blaze. Georgia-Pacific Spokesperson Eric Abercrombie tells KTRH four employees were airlifted to Memorial Hermann Hospital in Houston and remain hospitalized.  One is currently in fair condition and three are listed in critical condition.

The three other employees were released from a Lufkin area hospital.  Georgia-Pacific is based in Atlanta, their Corrigan plant manufactures plywood for buildings. The Occupational Health and Safety Administration (OSHA) is conducting an investigation to determine the cause of the explosion.