Four employees were injured in an explosion that damaged a building products mill in Thomasville, Ala. The blast occurred early Wednesday.

Officials with Louisiana-Pacific's Oriented Strand Board mill said the four were transported to a Mobile hospital for treatment.

Mary Cohn, a company spokeswoman in Nashville, declined to discuss the extent of the worker's injuries, but said they remained hospitalized.

The company said the explosion and fire occurred just before 2 a.m. in the thermal oil room and was brought under control in just under two hours.

Cohn said it's unclear what caused the explosion and it remains under investigation.

The mill manufactures sheathing used mainly in residential construction.