Six firefighters were treated in Reading Hospital for throat irritation suffered early Saturday while fighting a two-alarm fire involving chemical canisters that had exploded in a Robeson Township warehouse, officials said.

Portions of the roughly 5,000-square-foot cement block warehouse at 4371 Morgantown Road Route 10 south of Plowville sustained severe damage when chemical barrels, owned by ChemClene Corp. of Malvern, Chester County, blew up in the blaze.

The blasts sent up fireballs and a column of smoke visible for more than a mile, officials said.

Damage was estimated at $350,000. The fire started in the rear of the building, but a cause has not been determined, according to Trooper Michael J. Yeity, a state police fire investigator.

Neighbors were awakened shortly before 2 a.m.

“They heard a loud explosion and saw the flames,” said Geigertown Fire Company Chief Paul D. Shirey.

He was one of the first on the scene.

“It was a big ball of flames, and there were several explosions,” the chief said. “When they blew, you could feel it in your chest.”

About 200 volunteers worked to pour water on the flames, which were controlled about 4 a.m., the chief said.

Shirey could not tell how many explosions occurred.

“There were too many (to count),” he said.

There were no evacuations.

Treated in the hospital were Shirey, 33, and Geigertown firefighter Scott Gullo, 21. Also treated were Kulptown Fire Company volunteers Shawn Moyer, 27; Robert Erb, 48; Carl Doaty Jr., 21; and Christopher Carpenter, 29.

Yeity identified the building owner as Margaret A. Helms, 59, of the township.

Yeity listed three tenants. They were ChemClene; Norman C. Thomas, 59, of Robeson; and Newman C. Johnson, 58, Bowmansville.

The chemical drums that exploded belonged to the chemical company, according to Brian S. Gottschall, Berks County deputy coordinator of emergency management services.

ChemClene is a solvent recycling company, according to the state Department of Environmental Protection.

No one answered the office phone there Saturday.

Gottschall said county emergency workers went inside the burning building to assess the chemicals, then gave firefighters advice how to clean gear and prevent injury.

“We identified chemicals and we recommended use of personal protective equipment for them,” he said. “Everything was melted. Not all the materials were in steel drums. Some were in plastic.”

Officials did not release the names of the chemicals.

Firefighters stayed away from the walls of the building and poured water on the fire from 50 feet or more away, Shirey said.

Firefighters responded from the Geigertown, Birdsboro, Kulptown, Monocacy, Morgantown, Gibraltar, Reiffton, Stonersville and Brecknock Township in Berks County.

Firefighters also responded from the Churchtown and Goodville fire companies in Lancaster County; and the Elverson, Honey Brook and Martins Corner fire companies in Chester County, Shirey said.