The operator of a global network of radioactivity sensors said Monday its two Russian sites closest to a mysterious explosion on Aug. 8 went offline two days after the blast, raising concern about possible tampering by Russia.
The Russian Defense Ministry, which operates the two stations, did not immediately reply to a request for comment.
Russia's state nuclear agency, Rosatom, has acknowledged that nuclear workers were killed in the explosion, which occurred during a rocket engine test near the White Sea in far northern Russia.