INDIANAPOLIS -- The Sierra Club joined chemical weapons activists Tuesday in suing the Army over shipments of nerve agent waste from Indiana to Texas for incineration, alleging that the liquid waste is more hazardous than the military claims.

The federal lawsuit filed in Terre Haute alleges the shipments along more than 900 miles of highway through eight states pose "an imminent and substantial endangerment" to public health and the environment and violate state and federal laws.

It asks the court to halt shipments of the waste, which is being created by the ongoing destruction of the Army's stockpile in western Indiana of VX nerve agent, a Cold War-era chemical weapon so deadly only a tiny droplet can kill a human.

Mick Harrison, the plaintiffs' attorney, said Newport Chemical Depot workers have told activists the waste contains higher levels of VX and hazardous chemicals than the Army claims.

If that's the case, he said the VX hydrolysate being shipped in truck convoys from Newport to Port Arthur, Texas, could endanger residents along that route if there were an accident.

"It's a real recipe for disaster," Harrison said.

The Army contends the waste contains a minuscule amount of VX -- 20 parts per billion or less -- and is no more dangerous than other hazardous wastes shipped each day across the nation.

Army spokesman Greg Mahall said Tuesday that the Army does not comment on pending litigation and had not yet seen the lawsuit.

"We stand by our statements of the past. That's all I can say," Mahall said.

Last month, the Army signed a $49 million contract with Veolia Environmental Services to incinerate about 2 million gallons of the chemical waste, which is called VX hydrolysate.

That agreement came after two failed deals with Perma-Fix Environmental Services Inc., in Dayton, Ohio, and DuPont Co. in Deepwater, N.J. were abandoned because of strong opposition.

Ross Vincent, a senior policy adviser with the Sierra Club, said in a statement that the group is "baffled" by the Army's insistence on shipping the waste from the Newport depot to an out of state site for disposal. Activists have called for it to be treated onsite.

"They have wasted at least four years and untold millions of taxpayer dollars by attempting to put VX hydrolysate on the public highways and force it down the throats of a succession of distant unwilling communities," Vincent said.

As of Tuesday, 41 trucks have delivered a total of about 164,000 gallons of VX hydrolysate to Veolia's Port Arthur plant, said Mitch Osborne, the plant's general manager. So far, about 72,000 gallons of that waste had been incinerated at that complex.

Osborne said Veolia Environmental Services, a division of Paris-based Veolia Environnement, had not seen the lawsuit but believes the incineration of the waste is safe.

"We still are confident that there's no issues with the waste being managed at the our facility. We've got the permits and it's got none of the characteristics of the VX," he said. "We assume we will have a favorable outcome once this does make it to court."

The lawsuit was filed by the Sierra Club, the Berea, Ky.-based Chemical Weapons Working Group, Citizens Against Incineration at Newport, and Community In-Power Development Association, a Port Arthur group. Five residents in Indiana and Texas were also listed as plaintiffs.

The lawsuit alleges the Army and Department of Defense have violated the federal Resource, Conservation and Recovery Act, which it says permits citizens to sue if they believe actions by anyone, including the U.S. government, may endanger the public health or environment.

In May 2005, an Army contractor began destroying more than 250,000 gallons of VX stored at the Newport complex about 30 miles north of Terre Haute through chemical neutralization. As of Tuesday, about 51 percent of that stockpile had been destroyed.