BILLINGS, Montana: A lawsuit by environmentalists claims fire retardants dropped on forest fires should be restricted because of potential harm to rivers and lakes.

However, others have said restricting the use of flame retardants could put people and property at risk during forest fires in Montana.

The environmental group suing the US Forestry Service agency claims Montana is violating federal clean water laws because officials are not taking measures to protect streams and rivers.

In filing the lawsuit, Forest Service Employees for Environmental Ethics is seeking an injunction that prevents Montana officials from using aerial retardants until they receive a pollution permit.

While the Forest Service has acknowledged that fire retardants have been dropped into waterways more then 200 times over the past decade. They note that this represents less than 1 percent of the thousands of drops annually. They were also adamant that environmental damage from fires can exceed the pollution from retardants.

"The only way to prevent accidental discharges of retardant to waters is to prohibit its use entirely," government attorneys wrote. "Such a prohibition would be tantamount to a complete ban of aerial discharges of retardant."

Forest Service officials said they are trying to come into compliance with the law by obtaining a pollution permit, but that could take years.

"The Forest Service says it should be allowed to pollute, business as usual," said Andy Stahl, who leads the Eugene, Oregon-based group behind the lawsuit. "Our position is that business as usual is illegal."

A court ruling is expected after both sides have presented their arguments.