HARRISBURG — Prodded by the federal Environmental Protection Agency, Pennsylvania said it is expanding the scope of water tests to screen for radioactive pollutants and other contaminants from the state’s natural gas drilling industry.

The state Department of Environmental Protection’s acting secretary, Michael Krancer, wrote Wednesday to the EPA to say he has requested additional testing from some public water suppliers and wastewater treatment facilities.

Those steps, he said, were in the works before the EPA’s regional administrator, Shawn Garvin, sent a March 7 letter asking Pennsylvania to begin more water testing to make sure drinking water isn’t being contaminated by drillers. The state’s requests for additional testing, however, were made later in March, Krancer said.

The tests should check for radium, uranium and the salty dissolved solids that could potentially make drilling wastewater environmentally damaging, according to the letter.

In his letter, Garvin pointed out that most treatment facilities are unable to remove many of the pollutants in the drilling water.

Garvin also asked Pennsylvania to re-examine permits issued to the treatment plants handling the waste, saying they lacked “critical provisions.”

Krancer responded that requirements to monitor for substances of concern will be added to permits upon renewal and where warranted.

An EPA spokeswoman, Donna Heron, said Thursday that her agency is reviewing Pennsylvania’s letter.

“We will continue to work closely with the state of Pennsylvania on all the issues involving Marcellus Shale,” she said.

Shale drilling requires injecting huge volumes of water underground to help shatter the rock — a process called hydraulic fracturing. Some of that water then returns to the surface.

Pennsylvania allows partially treated drilling wastewater to be discharged into rivers from which communities draw drinking water.

Some Pennsylvania drilling wastewater is reused or trucked out-of-state for disposal underground. Of the wastewater that was taken to treatment plants in recent months, the great majority went to seven plants that discharge into rivers, including the Susquehanna.