Ottawa ? A weekend fire of suspicious origins caused more than $1 million worth of damage at the Ottawa Co-op, but it is not expected to derail area farmers who rely on the business.

Adrian Derousseau, general manager of the co-op, said Monday the business’ crop production division was badly damaged in the fire that began shortly before 11 p.m. Saturday. It destroyed the division’s offices and warehouse at 120 North Cedar St.

No one was injured in the blaze, but Derousseau said firefighters worked mightily to contain the building’s chemicals and pesticides from escaping into the adjacent Marais des Cygnes River.

“It was a rough fire to fight,” Derousseau said. “But if it happened 10 or 15 years ago, it would have been pretty serious. Chemicals were a lot more toxic back then.”

Richard Oglesby, assistant chief of the Ottawa Fire Department, said the blaze was one of the largest in the city in the past five years. Firefighters responded to the call at 10:55 p.m. and worked to bring the blaze under control until about 2 a.m. Damage was estimated at between $1 million and $3 million.

Firefighters entered the building but had to retreat after hearing two explosions, Oglesby said. A private contractor also was brought to the scene to build several small dikes in area ditches to prevent contamination of the river.

The cause of the fire had not been determined Monday. Larry Scott, a spokesman with the Bureau of Alcohol, Tobacco, Firearms and Explosives, confirmed department investigators were on the scene. But he said it was too early to say whether the fire had been intentionally set.

“It is being looked at,” Scott said. “I think they just need to do their analysis and scene work.”

Independent Fire investigator Alex Koenenm surveys the charred remains of the Ottawa Co-op. The cause of the fire, which broke out late Saturday, is under investigation.

Derousseau said the company already had taken measures to make sure area farmers who rely on the co-op to provide crop-spraying services would not suffer a delay in fieldwork during this critical time of year.

“It couldn’t have happened at a worse time of year because we’re right in the middle of spraying season,” he said. “But we’re operational. We could go out and do sprays today and not have any issues.”

The co-op owns all three of Lawrence’s grain elevators, and the facility housed the spraying equipment the company uses to service Lawrence-area farm fields.

The company expected to receive two new sprayers today and Wednesday to replace three sprayers lost in the fire. It also was receiving a new shipment of chemicals and pesticides. The company has rented new office and storage space in a building directly east of its former location.

A fire Saturday night caused between million and million in damages to the Ottawa Co-op.

Bill Wood, agriculture agent for the Douglas County Extension Service, said the co-op was the largest of only a handful of companies that provide spraying services in the county. He said now was a critical time of the year for spraying corn and soybean crops.

“There’s not a long time frame that you can spray in,” Wood said. “We still have a little bit of time, but we wouldn’t want to stretch it out too long.”

— Staff writer Eric Weslander contributed information to this report.