PARIS – Investigators from several agencies were in town Wednesday to begin an investigation into the cause of a fire that destroyed a SAD 17 bus earlier this month.

“They’re looking at things before they remove them,” said Superintendent Mark Eastman as the investigators began removing large amounts of charred fiberglass from the engine compartment.

The 2007 Thomas Freightliner was destroyed in early September as 10 to 15 students were about to board in the late afternoon. Some 200 students and six other buses were in the bus loop at the Oxford Hills Comprehensive High School at the time of the fire. No one was injured, but the bus was destroyed. A similar bus was taken off the road immediately and will not be used until the bus company, W.C. Cressey and Son Inc. of Kennebunk, can certify that it is safe.

Eastman said Wednesday that he expects the owner to give that certification as soon as Thursday.

Early indications are that the fire was electrical and began in the engine compartment, officials said, but investigators were mum about their work Wednesday. Eastman said John Maurus, a certified fire investigator from Probe Inc. of Chicago, who is representing the bus manufacturer Daimler Truck, told him he had signed a confidentiality agreement.

“They won’t tell us anything,” Eastman said.

Also on hand were Thomas Bush of New England Fire Cause and Origin Inc. of New Hampshire, which represents SAD 17’s insurance company, Massamont; and Steve Whitefield, a lead technician at Cressey.

The investigators went back and forth from the burned-out bus to the other similar bus comparing parts during their work.

“They are creating images back and forth,” Eastman explained. “They are looking at things before they remove them, then they dig a little deeper.”

The group is expected back at the site Thursday to complete their work.

Richard Soules, a transportation specialist for the Maine Department of Education, is also expected to be in Paris on Thursday, Eastman said.

“He’s been getting a lot of calls,” Eastman said of Soules’ interest in the investigation.

There was no indication when an official cause of the blaze would be released.