The fire on the Ekaterinburg submarine in December 2011 was, as it turns out, a very serious incident - the submarine had full complement of torpedos and missiles on board. Reports in the Russian press - Novaya Gazeta and Kommersant-Vlast - provide a detailed analysis of the situation quoting sources at the Northern Fleet and the Main Staff of the Russian Navy.
The torpedos were in an immediate danger - they were quite close to the fire. Missiles, however - various sources say the submarine had 16 or fewer missiles - were where the real danger was. The R-29RM missiles carried by Project 667BDRM submarines are liquid fuel missiles that are very vulnerable to a fire. Also, the missiles apparently carried nuclear warheads - the submarine was getting ready to go on patrol.