The first shipments of chemical waste from deadly VX nerve agent being destroyed in Indiana arrived at a Port Arthur, Texas, plant on Tuesday, hours before two activist groups called on the Army to immediately halt further shipments.

Four tractor-trailers pulled into Veolia Environmental Services' plant about 12:40 a.m. Tuesday, each loaded with a reinforced tank filled with about 4,000 gallons of VX hydrolysate, said Daniel J. Duncan, Veolia's environmental health and safety manager.

That convoy left western Indiana's Newport Chemical Depot early Monday for the nearly 1,000-mile journey to Port Arthur as part of a $49 million contract Veolia recently signed with the Army to incinerate about 2 million gallons of the chemical waste.

Duncan said about 10,000 gallons of hydrolysate will be incinerated later this week after additional shipments of the liquid waste arrives from Indiana.

Hours after those first trucks arrived in Port Arthur, however, two activist groups urged Army and Indiana officials to immediately halt further shipments to the southeast Texas city.

The letter from the Chemical Weapons Working Group of Berea, Ky., and Citizens Against Incineration at Newport said "multiple confidential sources" have told the groups that the waste may harbor more than twice the amount of VX the Army contends it contains.

Craig Williams, the Berea group's director, said the sources claim that although the Army maintains the hydrolysate contains no more than 20 parts per billion of VX, some samples of the waste stored at Newport had shown VX in concentrations of up to 48 parts per billion.

He said the sources, including someone claiming to work at the Newport disposal site, said those readings came from samples of hydrolysate that had to be transferred to a new storage tank at Newport due to leaks in the original container.

Williams said the claims may indicate that the VX -- a single droplet of which can kill a human in minutes -- is reforming after being neutralized in chemical reactors at Newport, located about 30 miles north of Terre Haute.

"Something is happening. We don't know what it is and frankly the critical issue isn't what's causing it. The critical issue is whether that's accurate" Williams said.

Jeff Brubaker, the Army's onsite manager at Newport, said he could not comment on the groups' letter because he had not seen the specific claims made by the individual who claims to work at the Newport site.

"Without having the actual letter with more specific references, there's really nothing to comment on," Brubaker said. "I have no information to make a comment on."

The Army contends the hydrolysate is no more dangerous than other hazardous wastes shipped each day across the nation.

Chemical weapons and community activists dispute that, saying the hydrolysate contains toxic chemical compounds and more VX molecules than the Army maintains. Those groups worry that an accident along the eight states the trucks are traveling through could spill the waste.

Hilton Kelley, the director of Port Arthur's Community In-Power Development Association, said Port Arthur has eight major oil refineries and three chemical plants, and residents there suffer from respiratory ailments and other maladies they blame on toxic releases.

"We are pretty upset about the fact that we weren't even given a notice about this shipment coming to our area. There was no public comment period or anything," Kelley said.

Duncan said Veolia's plan to incinerate the VX hydrolysate after mixing it with other water-based waste and chemical reagents poses no threat to the public.

Another Army contractor, Parsons Technology Inc., began work in May 2005 to destroy Newport's 250,000-gallon VX stockpile. As of Tuesday, that project was 49 percent complete.

Newport spokeswoman Terry Arthur said that about 706,600 gallons of hydrolysate was currently stored at Newport as of midnight Monday.