The radioactive-particle sensors of at least one of the stations in Russia that went offline after a mysterious blast in the country's far north are transmitting again, the operator of the global network to which they belong said on Tuesday. Four of the stations that scan for so-called radionuclide particles wafting through the air for the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) went silent in the days after the Aug. 8 explosion, which occurred during a rocket engine test. That fueled suspicions among nuclear analysts that Russia tampered with the stations, since it operates them.

The blast killed five employees of Russia's nuclear agency Rosatom but Moscow has not explained why the incident caused a spike in radiation levels in a nearby city. U.S.-based nuclear experts suspect Russia was testing a nuclear-powered cruise missile. "RN stations RUP 56 (Peleduy) and RUP 57 (Bilibino) have resumed operations in Russia & are currently backfilling data," CTBTO chief Lassina Zerbo said on Twitter, using an abbreviation for radionuclide. He added that there had been "excellent cooperation and support from our Russian station operators." Bilibino is one of the four stations that the Vienna-based CTBTO said on Monday had gone offline in the days after the explosion, though it is in Russia's Far East, a long way from the site of the accident. Peleduy had not previously been mentioned in relation to the blackouts. The CTBTO did not immediately respond to a request for an update on the status of its Russian stations. The CTBTO's website lists seven radionuclide stations in operation in Russia, with another under construction. The two closest to the blast site went offline two days after the explosion, just before any particles from the blast are likely to have reached them, according to a simulation Zerbo posted.

To requests on #IMS detection beyond #CTBT, data in, or near the path of potential plume from the explosion are being analyzed . We’re also addressing w/station operators technical problems experienced at two neighboring stations. All data are available to our Member States. https://t.co/pHL4WrHU23 pic.twitter.com/9aO5cQTlls — Lassina Zerbo (@SinaZerbo) August 18, 2019