SAN JUAN, Puerto Rico  _ Environmentalists demanded Tuesday that Puerto Rico’s government order new tests to determine whether coal ash being used for home and road construction in the U.S. island’s south is free of toxic material.

Activists contend the global energy company AES Corp. is selling coal ash containing lead, arsenic and mercury to developers who are using it for residential and transportation projects.

Several municipalities are considering moratoriums on such projects following complaints from residents, and scientists say the government should start testing air and water for possible contamination.

“This is a recipe for disaster,” environmental scientist Neftali Garcia Martinez told reporters. “No one has done any tests to see how these places are being affected.”

Allan Dyer, president for AES Puerto Rico, denied the ash is contaminated. He said the ash product, Agremax, that the Arlington, Virginia-based company sells as filler material for construction projects has been thoroughly tested and complies with local and federal regulations.

“Agremax is safe and nontoxic, and represents no harm to the health of the community or the environment,” he said in a statement.

Pedro Nieves, president of Puerto Rico’s Environmental Quality Board, said the use of coal ash for such projects is authorized because federal studies have shown that heavy metal levels are within safety standards. But he said the agency is collecting information and might issue a new round of studies if needed.

“We are not standing around with our arms crossed,” he said.

In December, the U.S. Environmental Protection Agency delayed a decision on whether to propose reclassifying coal ash as hazardous, which would limit where it could be sent for disposal. The issue was raised when 5.4 million cubic yards of coal ash spilled in Tennessee in 2008, creating one of the worst environmental disasters of its kind in U.S. history.

Nieves said he is monitoring the debate and might change his stance if the EPA issues new regulations.

It is the second time in recent years that AES has faced concerns from environmentalists and government.

In 2007, the company agreed to pay $6 million to clean up industrial waste in the Dominican Republic, whose government filed a lawsuit alleging AES dumped 82,000 tons of coal ash along several beaches.

The lawsuit claimed the ash was shipped from the AES plant in Puerto Rico, which started operating in 2002.