DURANGO, Colo. — The Animas River is the cultural soul of this patch of southwestern Colorado, a sort of moving Main Street that hosts multiple floating parades a year and is typically bustling with rafters and kayakers. Schoolchildren study the river. Sweethearts marry on its banks. Its former name, given by Spaniards, is el Río de las Ánimas, the River of Souls.

But since Wednesday, the Animas has been grievously polluted with toxic water spilled from one of the many abandoned mines that pockmark the region — a spill for which the has claimed responsibility, saying it accidentally breached a store of chemical-laced water.

On Sunday, anger over the spill boiled over after the agency announced that the amount of toxic water released was three times what was previously stated — more than three million gallons rather than one million — and that officials were still unsure if there was a health threat to humans or animals.

The day of that announcement, State Senator Ellen Roberts, a Republican who lives near the river, cried softly as she considered the pollution, adding that she had dropped her father’s ashes in the depths of the river, which pollutants had turned into an unnatural-looking yellow-orange ribbon.

“It is not just a scenic destination,” Ms. Roberts said. “It is where people literally raise their children. It is where the farmers and ranchers feed their livestock, which in turn feeds the people. We’re isolated from Denver through the mountains, and we are pretty resourceful people. But if you take away our water supply, we’re left with virtually no way to move forward.”

On Monday, Gov. John W. Hickenlooper released $500,000 in funds for assistance. The City of Durango and La Plata County have declared states of emergency.

Soon after the spill was detected, city officials stopped pumping water from the Animas into the reservoir that provides drinking water for Durango’s 17,000 residents — taking action swiftly enough that the contamination did not reach the drinking supply. The reservoir still receives water from the Florida River, a tributary of the Animas, but the city has asked local residents to conserve so that the reservoir does not get too low.

Most people living outside the city use wells, and officials say about 1,000 residential water wells could be contaminated.

The river is closed indefinitely, and the county sheriff has hastily recast his campaign signs into posters warning river visitors to stay out of the water. The yellow plume has traveled down to New Mexico — where officials in several municipalities have stopped pumping river water into drinking water systems, fearing contamination — and to the Navajo Nation.  

Testing by the E.P.A. — an agency typically in the position of responding to toxic disasters, not causing them — found that the wastewater spill caused levels of arsenic, lead and other metals to spike in the Animas River.

On the day of the accident, a team from the agency had been investigating an abandoned mine about 50 miles north of here. Called the Gold King, it is roughly 1.5 miles long and about 700 feet tall at its highest point. The mine had been abandoned for nearly a century, but between roughly 1890 and 1920 it produced 350,000 ounces of high-grade gold, according to its owner.

For years, the Gold King has leaked toxic water at a rate of 50 to 250 gallons a minute. The agency had planned to find the source of the leak in the hope of one day stanching it. Instead, as workers used a backhoe to hack at loose material, a surprise deluge of orange water ripped through, spilling into Cement Creek and flowing into the Animas. The burst did not injure workers.

In his first interview since the spill, the owner of the mine, , said the spill was probably the fault of another mine company — the Sunnyside Gold Corporation — that had built retention walls inside an abandoned mine near the Gold King, part of an old cleanup agreement with the federal government. Once the Sunnyside mine filled with wastewater, the water probably spilled into the Gold King, and then into the Animas, Mr. Hennis said.

He urged Sunnyside’s parent company, the , to clean up the mess. “They’ve got to step forward and be responsible,” he said of Kinross. A spokesman for Sunnyside, Larry Perino, said the company had no role in Gold King spill.

Since the 1870s, metal mining has both enriched and poisoned this region, turning the earth under portions of southwest Colorado into a maze of tunnels and leaving behind shuttered sites oozing with chemicals. There are about 200 abandoned mines in the Animas watershed. Sunnyside was the last to close, in 1991.

On Sunday night, residents packed a school auditorium in Durango for a meeting with the E.P.A.’s regional director, Shaun McGrath. During a public comment session that lasted more than two hours, residents flouted a sign on the wall that instructed the auditorium’s typical patrons — middle schoolers — to refrain from calling out, jumping up or insulting others during assemblies.

Shouts rang out. A few people cried. One resident questioned whether the agency had refashioned itself into the “Environmental Pollution Agency.” Others demanded to know what would happen to wildlife, livestock, water wells, sediment and river-based jobs.

“When — when can we be open again?” asked David Moler, 35, the owner of a river-rafting company who had approached a microphone. “All I hear is a handful of ‘gonna-dos,’ ” he added. “What should I tell my employees?”

Mr. McGrath and his colleagues urged patience and assured residents that they would provide information about health risks once they had it. The agency, he said, is awaiting test results to determine whether the water poses a risk.

“We’re going to continue to work until this is cleaned up,” Mr. McGrath said, “and hold ourselves to the same standards that we would anyone that would have created this situation.”