HELENA, Mont. - Missoula County and three environmental groups filed a lawsuit Friday asking a judge to prevent an oil company from hauling oversized equipment through Montana to the oil sand fields in Alberta, Canada.

The plaintiffs allege state transportation officials violated the Montana Environmental Protection Act by approving the shipments without properly analyzing the effect on the state and without studying alternative routes.

The lawsuit claims the state agency should have done a full environmental impact statement and did not provide important information relevant to the project during the public comment period.

Montana Transportation Director Jim Lynch said Friday his agency complied with the state's environmental law in approving the project.

"The Montana Environmental Protection Act sets the process in place and that's what the Montana Department of Transportation followed," he said.

Transportation officials have not yet issued permits for the big loads' transport, but that's just a formality at this point, Lynch said.

The lawsuit was filed in Missoula District Court by the county, National Wildlife Federation, Montana Environmental Information Center and Sierra Club.

It asks the court to prevent Montana transportation officials from issuing permits for the shipments until a full environmental impact statement is completed and all alternatives are analyzed.

"The agency's review of the project failed to take a hard look at all the impacts of the construction and use of an industrial corridor that runs along some of Montana's most treasured rivers and streams, and through our scenic mountains and rural Montana," Sarah McMillan, an attorney with the Western Law Environmental Center, said in a statement.

Imperial Oil, a subsidiary of Exxon Mobil Corp., originally applied to ship 207 of the 30-foot-tall loads across Idaho and Montana during the next year to the Kearl Oil Fields in Canada.

The company is reconfiguring the first 33 loads into 60 smaller shipments that can move on interstate highways. The downsizing is an attempt to mitigate costs from the delay in obtaining permits from Idaho and Montana, the company said in February.

The company also is still trying to get state permits to truck the 30-foot-tall megaloads along the original route.

That plan would move the loads by truck across Idaho on U.S. 12 to Lolo Pass. From there, the shipments would make their way through Missoula, head east on U.S. Highway 200 then north along the Rocky Mountain Front, taking several highways to the Canadian border at Sweet Grass.

Work is still under way to build or improve turnouts, raise or bury power lines and install traffic signals and signs, Lynch said.

The plaintiffs said they are concerned the changes to those highways to accommodate the loads would create a permanent corridor for oversized loads.