A team of hazardous-waste investigators and a radiation specialist plan to inspect a decommissioned building in Bethpage this week where Grumman Aerospace Corp. once had an area for “radiation effects studies.”

The state Department of Environmental Conservation said late Tuesday the team will examine the interior of the 60,000-square-foot building known as plant 26, which once also housed a U.S. Department of Defense “black room” that required security clearance for entry.

Earlier in the day, Sen. Chuck Schumer (D-N.Y.) formally asked the U.S. Environmental Protection Agency to help state and local officials do a top-to-bottom investigation of plant 26, as well as to provide support, technical assistance and resources to examine present and past use of radioactive materials on the site formerly used for research and manufacturing by the Navy and Grumman, which became Northrop Grumman in 1994.

Both developments came after Newsday reported last week that dozens of radioactive isotopes were handled at Grumman facilities from 1960 to 2015, according to a report that the defense contractor filed with the DEC in October. The state environmental agency had ordered the report after elevated levels of radium were measured at a Bethpage Water District well.

The report, filed in October, was obtained under a Freedom of Information Law request filed by Newsday. It later was made public.

“The source of alarming levels of radium recently detected must be identified as soon as possible so any appropriate remedial and defensive action can be undertaken to protect the public health and environment,” Schumer wrote in a letter sent Tuesday to EPA Administrator Scott Pruitt.

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The EPA and Northrop Grumman did not respond to requests for comment.

The Navy and Grumman researched, manufactured and tested aviation and space exploration vehicles on a Bethpage parcel of more than 600 acres starting in the late 1930s. The site has a long history of soil and groundwater contamination, is on the state Superfund list and is subject to a number of cleanup plans.

Earlier this month, monitoring wells on the grounds of nearby Bethpage High School detected levels of total radium as high as 25 picocuries per liter. The safe drinking water standard is 5 picocuries per liter. State health and environmental officials said no one was exposed to the water, because the area’s drinking water is supplied by the Bethpage Water District.

The DEC could not immediately provide more details about what the probe of plant 26 would involve.

Last week, Newsday reported that an environmental assessment of plant 26 in 2000 said that alpha, beta and gamma radiation was used to test the strength of metals.

That confidential document was turned over to Newsday by concerned residents.

“It is terrific that DEC is sending experts that understand radiological issues,” said James P. Rigano, a Melville environmental attorney speaking on behalf of those residents. “The citizens I have been working with are delighted that the radiological issues are now Page 1 news.”

Judith Enck, who served as EPA regional administrator covering New York until early this year, said the federal agency could declare the properties a federal Superfund site and divide work among federal and state authorities to cover more ground. The state would have to nominate the site for consideration, she said.

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“The key is to get Navy and Grumman to be more proactive and put on an aggressive schedule to deal with their legacy of pollution on Long Island,” Enck said.

The state previously said testing for radioactive materials had not been done because there was no indication they were used in manufacturing. Last week, the DEC ordered Northrop Grumman to turn over more documents about the “form, nature and ultimate disposition” of radioactive materials used at the site, DEC spokesman Sean Mahar said.

Bethpage Water District Superintendent Mike Boufis welcomed the additional scrutiny.

“I think if you have multiple agencies doing the testing or splitting up duties, it will go much faster,” he said.