Captain Sergei Pavlov, an aide to the commander of Russia’s navy, praised the heroism of the men, who died as they battled to stop the fire from spreading in the submersible.

“With their lives, they saved the lives of their colleagues, saved the vessel and prevented a planetary catastrophe,” he said at the funeral Sunday attended by the navy chief according to the Fontanka news service.

Kremlin spokesman Dmitry Peskov said he wasn’t aware of the official’s comments but said there was no indication the incident posed a broader threat. “As for the reactor, there are no problems with that,” he said on a conference call.

Russia broke three days of secrecy July 4 and confirmed that the stricken underwater research vessel was nuclear-powered. Defense Minister Sergei Shoigu told President Vladimir Putin in a meeting shown on state TV that the nuclear reactor on board the vessel had been completely sealed off.