BILLINGS, Mont. — Site investigations and some cleanup work at 10 polluted mining complexes in four states were suspended because of conditions similar to those that led to a massive wastewater blowout from an inactive Colorado gold mine, U.S. Environmental Protection Agency officials said.

The sites include three in California, four in Colorado, two in Montana and one in Missouri, according to details obtained by The Associated Press.

They have the potential for contaminated water to build up inside mine workings, EPA Assistant Administrator Mathy Stanislaus said. That would set the stage for a possible spill such as last month’s near Silverton, Colorado, where an EPA team triggered a 3 million gallon blowout of toxic sludge while doing excavation work on the inactive Gold King Mine.

The accident fouled rivers in three states and attracted harsh criticism of the EPA for not being prepared despite prior warnings that such a spill could happen.