Days after a mysterious explosion at a Russian naval test site caused radiation detectors to briefly spike, silence at several monitoring stations has raised fears that Moscow is hiding the extent of the blast that killed five people.

Officials at the Vienna-based Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) said on August 20 that two nuclear monitoring stations in Russia have resumed operations after mysteriously halting the transmission of data. The CTBTO did not comment on the other two stations which it previously said had gone silent in the aftermath of the accident. Russia has a total of six stations, which scan for so-called radionuclide particles wafting through the air.

“RN stations RUP 56 (Peleduy) and RUP 57 (Bilibino) have resumed operations in Russia & are currently backfilling data,” Lassina Zerbo, executive secretary of the CTBTO, said in a message on Twitter. 

“Excellent cooperation & support from our Russian station operators under ‘The Provisional Operation Status of the IMS,'” he added, referring to the International Monitoring System that collects and monitors data worldwide on radiation in the atmosphere.

Kremlin spokesman Dmitry Peskov told reporters on August 20 that while the president receives information “about everything,” the monitoring stations were “outside our purview.”

“As for the operation of the stations, frankly, I don’t know who they report to. It is easier for you [journalists] to find who they report to and request information directly as to why some data is or is not being transmitted,” Peskov said.

“But, so you understand, the head of state is receiving complete updates about what is going on out there,” he added.