A fire briefly rekindled but was suppressed by South St. Paul firefighters Thursday afternoon in the remains of a chemical plant that was gutted a day earlier, officials said.

Authorities had received no reports of people harmed by the explosive fire that destroyed the Epoxical Inc. plant Wednesday. But the Minnesota Pollution Control Agency (MPCA) was still monitoring the air and taking samples from the nearby Mississippi River, which received runoff from fire hoses.

The towering fire generated thick black smoke and toxic fumes that led to the evacuation of more than 1,500 workers from area businesses. Some schools delayed students from walking home and canceled sporting events. Businesses were allowed to reopen Thursday morning.

The fire's cause is still unknown, said John Ehret, chief of the West St. Paul Fire Department, which assisted and is merging with its South St. Paul counterpart.

"At this time, there is no reason to believe anything other than [an] accidental [cause] has taken place," Ehret said. He said fire investigators are interviewing employees to try to discover a cause and were waiting for a structural engineer to declare the charred hull, which had lost its roof, was safe to enter.

"We are just fortunate that nobody got hurt. The environmental stuff, we can manage that," said Jason Moran, MPCA incident commander.

The St. Paul Fire Department sent a hazardous materials team to the scene Wednesday to test the air for toxicity. The team detected nothing or negligible levels, said Mike Hogan, a St. Paul deputy fire chief.

Workers from the state Occupational Safety and Health Agency on Thursday talked company managers and employees. "We opened our investigation this morning," said OSHA spokesman James Honerman. "We are trying see what events led up to fire."

State OSHA records show Epoxical, which makes adhesives and other products, was cited in early 2003 for not having an adequate emergency response plan. It was directed to develop a plan that included evacuation routes and procedures.

The company also was cited at that time for not having a respiratory protection program for employees and for not properly training them to deal with a spill in their plant, where thousands of gallons of flammable, hazardous chemicals were mixed and stored.

Honerman noted the company quickly trained its employees, corrected the problems and paid a reduced fine of $840 by May 2003.

Fire Chief Ehret said Epoxical's plant manager did an excellent job of getting the 23 workers safely out of the burning plant and making sure all were accounted for so firefighters didn't need to enter the dangerous building to look for workers.

On Wednesday, the South St. Paul schools superintendent expressed alarm that police didn't notify schools about the fire. Police Chief Mike Messerich said that was because no schools were in the path of the smoke plume. However, he agreed the schools should have been called.

Officials said area businesses whose buildings or vehicles had soot on them can contact Epoxical to get the names of contractors to test and remove the soot.

Dave Hoeffel, whose family owns the business, estimated about $2 million in damage was done to the building, plus the loss of its contents.

Epoxical has a temporary office a block from its burned-out building. Hoeffel said the family is assessing how to get the business going again.

Jim Adams • 612-673-7658 • jadams@startribune.com