Russia is trying control the flow of publicly available information on Monday’s tragic submarine fire incident in the Barents Sea, which killed 14 sailors on board a deep-sea submersible, which is reportedly nuclear powered.

The Russian government refused to reveal more information on the vessel, calling it a "state secret" and said the information will not be made public as it's now classified.

Russian spokesman Dmitry Peskov said the Supreme Commander-in-Chief has all the information. “But this data cannot be made public because this refers to the category of absolutely classified data,” Peskov said. “There is classified information, this top secret is kept in the interests of a state and national security,” he explained.

Brushing off media comments that the submersible had a nuclear reactor on board, Peskov said it was a matter for the Russian Defense Ministry. A Russian online news platform said the fire occured on the nuclear-powered AS-12 Losharik, which is a relatively new ship. According to Fox News, the vessel was involved in research intended to prove Russia’s claims on the vast Arctic seabed in 2012.

Kremlin’s Defense Ministry in a statement said the vessel had unexpectedly caught fire while the it was measuring sea depths in Russia’s territorial waters. “Fourteen submariners died in a fire that broke out aboard a deep-sea underwater research vessel in Russian waters on July 1. The accident occurred while the submersible was conducting bathymetric measurements, namely examining the sea bottom, currents and depths,” it said.

Russian scientists are developing an advanced automated submarine that will be powered by an external combustion engine. In this photo, the Russian submarine Dmitry Donskoy (NATO-Typhoon class), the world's largest in active service, arrives at Kronstadt Navy base, outside Saint Petersburg, to take part in the Naval military parade, July 26, 2017. Getty Images/ OLGA MALTSEVA

Local Russian publications have stoked speculations by saying that the submersible was attached to military unit 45707 near St. Petersburg. The Independent describes this base as that of one of the most secretive military units in Russia and part of the defence ministry’s chief directorate of deep-sea research. Furthermore, the rush to categorize the incident as classified is in line with the unfoldment of events during the sinking of the Kursk nuclear-powered submarine in the same Barents Sea nearly 20 years ago.

Russian officials have not revealed the exact number of sailors on board during the incident and the number that survived. Details about the cause of the fire have also been suppressed. According to the Independent, Moscow said the fire was extinguished by the "heroic actions" of the crew.

Russian President Vladimir Putin, after a meeting with Defence Minister Sergei Shoigu on Tuesday, confirmed that seven first-rank captains were among the dead, including two who had received Russia’s highest "Hero of Russia" decoration.