HARRIMAN - Workers face "several weeks' worth of work" to clean up 2.6 million cubic yards of fly ash dumped across hundreds of acres after a retention pond collapsed early Monday morning at the Tennessee Valley Authority's Kingston steam plant.

No injuries have been reported, but one house was swept off of its foundation and onto the road, and huge piles of a mixture of water, mud and ash covered Swan Pond Road in Roane County.

"We've got a mess," said Tom Hamby of the Roane County Highway Department. "The problem is, you don't know what's under this stuff."

Officials say up to 400 acres of land adjacent to the plant are under 4 to 6 feet of material. An initial estimate projected that 2.6 million cubic yards of fly ash were released, said Laura Niles, an Environmental Protection Agency spokeswoman in Atlanta. Niles said the pond is reported to contain more than 40 million gallons of water, but she said that was an initial report. She added that the agency doesn't know how much water was actually released.

Some of the material made its way into Watts Bar Lake, which flows past the plant, and water flow through Melton Hill and Watts Bar dams has been reduced to prevent pollution from the flood, according to TVA spokesman Gil Francis.

"It's going to take some time to clean up," Francis said. "Crews are working 24/7."

Francis said 30 pieces of heavy equipment were being brought in, and about 100 people are involved in the cleanup effort.

Eight to 10 homes were flooded, and 12 residences in all have been affected by the break. Francis said an undetermined number of customers are without power.

"I am still in shock," Crystell Flinn, 49, told The Associated Press. Flinn's house was pushed off its foundation and driven more than 30 feet onto a road. "I don't think it really has hit me yet."

The 40-acre pond was used by TVA as a containment area for ash generated by the coal-burning steam plant, Francis said. An earthen wall gave way just before 1 a.m., flooding the road and railroad tracks leading to the plant.

No one was seriously injured or needed to be taken to the hospital, said Howie Rose, the director of the Roane County Office of Emergency Management and Homeland Security.

Rose said workers have repaired a ruptured gas line in the area. Also, he said, water quality testing is under way downstream, but so far "nothing above normal has been found yet."

Fly ash contains heavy metals. TVA is using a helicopter to assess the damage, and the agency is formulating a plan for the removal of the material, Francis said. The goal, he said, is to "restore the area to the way it was before (the flood)."

The Red Cross set up a shelter Monday in the Roane State Community College gymnasium to receive residents forced out of their homes. Six people stayed in the shelter temporarily until they moved to the Holiday Inn Express in Harriman, where, Rose said, TVA has arranged for them to stay.

Rose said a train carrying coal to the plant reached the point on the tracks that was flooded and couldn't go forward or back up. Officials were able to bring in another engine and back the train out of the area about 10:30 a.m.

Joey Shanahan, an assistant foreman with the Roane County Highway Department, said he arrived at the scene about 1 a.m. and was diverting traffic when the wreck occurred.

"About 2 or 2:30 (a.m.), the train came around the curve and couldn't get stopped in time," he said.

Three roads into the area have been blocked off, Hamby said, adding that officials weren't sure about the extent of the spill until daybreak.

The Environmental Protection Agency was notified, Francis said. Investigators are still trying to determine exactly what caused the flood, but he said heavy rains and freezing temperatures may be to blame. The National Weather Service reported it was only 14 degrees just before 6 a.m. Monday in Harriman.

According to Francis, the area usually receives about 2.8 inches of rain in December. There's been about 4.9 inches of rain so far this month, Francis said.

The flood buried and mangled the railroad tracks used by trains bringing coal to the plant. Rose said TVA has "a few weeks' " worth of coal on the ground.

Stationed at the base of one of the huge piles of wet fly ash, Hamby looked out over acres of debris.

"I've been here a long time," Hamby said, "and this is the worst thing I've experienced."