WASHINGTON (Reuters) - Republicans in the U.S. House of Representatives on Wednesday sought information from the Defense Secretary about lawsuits filed by nonprofit environmental groups against his department, as they probed possible foreign influence on such groups.

“We are interested in environmental litigation by U.S. based 501(c) organizations against the Department of Defense and its negative impact on our national security,” House Natural Resources Committee Chair Rob Bishop and oversight subcommittee Chair Bruce Westerman wrote in a letter to Defense Secretary James Mattis.

While some of these lawsuits “represent sincere and justified concerns about the effect of federal actions on the environment,” they said “foreign adversaries” can use those lawsuits as a tool to “reduce U.S. defense capabilities.”

The letter comes a week after the lawmakers wrote to the head of nonprofit the Natural Resources Defense Council (NRDC) to demand documents about its relationship with the Chinese government, accusing it of possibly “being influenced or coerced by foreign interests.”

The House Committee on Natural Resources is monitoring several other environmental groups and “will seek inquiry as appropriate,” a committee spokeswoman said in an email.

In Wednesday’s letter, the lawmakers pointed to lawsuits by the NRDC dating back to the 1990s that aimed to stop the use of sonar and underwater explosives by the Navy because of its impact on mammals. They said environmental litigation has restricted Navy training exercises and testing, and jeopardizes its ability to detect diesel electric submarines by China.

The lawmakers also cited a lawsuit by the Center for Biological Diversity that aimed to block the relocation of a Marine Corps air station in Japan because of its potential harm to a marine mammal, the Okinawa dugong. A court hearing on that case is scheduled for June 28.

Peter Galvin, co-founder of the Center for Biological Diversity, said in an email that House Republicans are targeting green groups’ international connections at a time when they should be investigating the Trump administration.

“So they’re going to ignore the Trump connections with the Russians and go straight to investigating efforts to save endangered wildlife like the Okinawa dugong? It’s an anti-wildlife agenda in search of a wild conspiracy theory,” Galvin said.

Earlier this year Bishop targeted outdoor retailer Patagonia for its web campaign opposing the Interior Department’s decision to reduce the size of two Utah national monuments, Bears Ears and Grand Staircase Escalante, calling the company a “special interest group.”