CHAMPAIGN – Two men hurt in Wednesday`s explosion at the Interstate Research Park in Champaign have been transferred to a hospital in Springfield.

Two employees for Huls Construction Co. of Gifford were moved Thursday from Carle Foundation Hospital in Urbana to the regional burn unit at Memorial Medical Center, 800 N. Rutledge St., Springfield.

The two men were cleaning out a 5,000-square-foot vacant area on the south side of the 50,000-square-foot Wayne H. Choe Technology Center, 1401 Interstate Drive, and working on interior finish, flooring and walls in preparation for a new occupant.

When the men used a fire extinguisher to put out a small blaze that started while they cut a pipe with an acetylene torch at 3:30 p.m. Wednesday, they were rocked by an explosion.

Cerion Technologies, a former occupant of the building, made computer drive disks and had left what investigators believe was magnesium dust in dust collectors.

Investigators theorized that the force of the fire extinguisher spray kicked loose magnesium dust into the air and set off a dust explosion.

Meanwhile, a former Cerion employee Friday questioned the presence of magnesium dust in the building.

Mike LaPointe of Champaign said he believed that aluminum dust, not magnesium dust, may have been involved in Wednesday's blast.

"Cerion Technologies was manufacturing aluminum disk substrates for use in the manufacture of hard disk drives for the PC and server markets worldwide," LaPointe said. "They were grinding down aluminum disks, so there could be aluminum powder. There was also a small operation manufacturing photo transfer drums for copier machines. I believe these were also aluminum."

Seven fire department trucks and six to eight police units responded, according to Champaign Fire Department spokeswoman Dena Schumacher.

When the first firefighters arrived, they found a fire, extensive damage to the rear of the building and two injured people. White smoke was showing toward the back of the building.

The explosion destroyed much of the south wall of the building and raised a portion of the roof by a few inches. Firefighters extinguished the blaze within two minutes.

Schumacher said a structural engineer has determined that the rear third of the building will need to be demolished as a result of the explosion.

An investigator from an insurance company was at the site Friday and was working on a damage assessment, Schumacher said.

The owner of the building, Wayne H. Choe, described the two victims as hard workers.

"My heart goes out to their families after what happened," Choe said. "Even though they weren't my employees, I feel bad that they had to experience this ordeal."

Choe said that he was unaware of metal dust of any kind, whether it be aluminum or magnesium.

"When I purchased this building, I received a Phase I environmental report that said the building had no hazardous materials," Choe said. "I hope that the investigators will eventually determine the real cause of the explosion."

Marshall Huls, the owner of Huls Construction, could not be reached for comment.

You can reach Tim Mitchell at (217) 351-5366 or via e-mail at tmitchel@news-gazette.com.