DENVER » An eerie yellow sludge that poured out of a shuttered gold mine and into a southwestern Colorado river was inching its way downstream toward New Mexico and Utah.

Federal officials said Friday the spill contains heavy metals including lead and arsenic, but it was too early to know whether they posed a health risk. No health hazard has been detected, but the tests were still being analyzed, said Joan Card, an adviser to Environmental Protection Agency Regional Director Shaun McGrath.

The spill also contained cadmium, aluminum, copper and calcium, the EPA said. The concentrations were not yet known.

An EPA-supervised cleanup crew accidentally unleashed 1 million gallons of the wastewater from the Gold King Mine on Wednesday, and it flowed down Cement Creek and into the scenic Animas River, which is popular with boaters and anglers.

The EPA warned people to stay out of the river and to keep domestic animals from drinking from it. Local officials declared stretches of the river off-limits in Colorado and New Mexico.

At least two of the heavy metals can be lethal for humans in long-term exposure. Arsenic at high levels can cause blindness, paralysis and cancer. Lead poisoning can create muscle and vision problems for adults, harm development in fetuses and lead to kidney disease, developmental problems and sometimes death in children, the agency said.

Water samples were also tested in New Mexico, but no results had been released. The Animas flows into the San Juan River in New Mexico, and the San Juan flows into Utah, where in joins the Colorado River in Lake Powell.

Officials said the contamination would likely settle into sediment in Lake Powell. Glen Canyon National Recreation Area officials said visitors will be warned starting Monday to avoid drinking, swimming or boating on affected stretches of the lake and river until further notice.

New Mexico officials were angry they were not told of the spill until Thursday, nearly a day after it occurred. "New Mexico deserves better," state Environment Secretary Ryan Flynn said.

McGrath apologized for the EPA’s response and for previously sounding cavalier about the concerns for public health and the environment. "Our initial response to it was not appropriate in that we did not understand the full extent of what we were looking at here," he said.

At least seven water utilities shut down their intake valves ahead of the plume to keep it out of their systems, and no drinking-water contamination was reported. Farmers also closed the gates on their irrigation ditches to protect their crops.

Water was still spilling from the mine on Friday, but officials didn’t know how fast. Crews were building containment ponds to catch it.

Card said the EPA has no way to get the discolored water out of the river and that it will eventually dissipate. It wasn’t clear when that will happen.

Officials were releasing extra water from at least one reservoir to help dilute the pollution.

Few details have been released about the spill, except that the cleanup crew of EPA employees and contractors accidentally breached a debris dam that had formed inside the mine. The crew was trying to enter the mine to pump out and treat the water, EPA spokeswoman Lisa McClain-Vanderpool said.

The mine has been inactive since 1923.