US lawmakers are calling for the Department of Energy to release documents detailing the targeting of American nuclear laboratories by Russian hackers last year.
The call - issued Thursday by the Republican chairmen of the House of Representatives' oversight and science committees - follows a Reuters report last month that the Russian hacking group known as Cold River targeted the Brookhaven, Argonne and Lawrence Livermore national laboratories over the summer.
"Although it is unclear whether the attempted intrusions were successful, it is alarming that a hostile foreign adversary targeted government labs working on scientific research critical to the national security and competitiveness of the United States," House Committee on Oversight Chairman James Comer and House Committee on Science Chairman Frank Lucas said in a joint statement released to reporters.
The Department of Energy - which is responsible for America's nuclear labs - said it had "not found any evidence of information being compromised."
Russia's embassy in Washington did not immediately return messages seeking comment.
Moscow has previously criticised the Reuters report, calling it anti-Russian propaganda.
Cold River, the Russian hacking group blamed for the intrusion efforts, has drawn increasing attention amid the conflict in Ukraine.
Last week, British authorities released an alert that accused the group of being behind an expansive and ongoing espionage campaign that has struck targets in government, politics, academia, defense, journalism and activism.