POSTVILLE, Iowa (AP) -

Three people were injured in an explosion at the Industrial Laminates/Norplex, Inc.  laminate manufacturing plant in Postville, Iowa, at about 1:15 a.m. Monday.

When firefighters arrived on scene, there was a medium amount of blue smoke rolling out the side of the building, with some lighter black smokeon the roof.

Postville Fire Chief Jeffrey Bohr said firefighters helped maintenance personnel inside the building to put out smaller fires and shut down necessary gas valves, boilers, and valves which transfer explosive/flammable materials used in the plants manufacturing process.

Chief Bohr said three people were injured in the explosion. One person, who was in critical condition, was transported by ambulance to the local hospital and later airlifted to the University of Iowa Hospital's Burn Unit in Iowa City. A second person was transported to a local hospital and was treated and released. A third person refused treatmentat the scene.

"Our prayers are with our employees and their families," said IndustrialLaminates/Norplex, Inc. said in a statement.

The Postville fire department says the explosion and fire caused an estimated $5-7 millionin damages. The Iowa State Fire Marshall will be investigating the explosion and fire.

The Postville Fire Department was assisted by the Postville Area Ambulance Service, Monona Ambulance service, Luana Fire Department, Decorah Fire Department's aerial truck, Postville Police Department, Allamakee County Sheriff, Allamakee County Emergency Management, and the Iowa State Fire Marshall'sOffice.