Sixteen apartments in downtown Moscow were engulfed by flames over what city authorities said was a malfunction in the gas system, Interfax reported Monday.
Eleven of the apartments were gutted entirely, Deputy Mayor Pyotr Biryukov said, adding that the city will foot the repairs bill.
Another 50 apartments in the Presnensky district were also damaged by the fires on Sunday, Biryukov was cited as saying.
Two people were hospitalized in severe condition with respiratory tract burns, the TASS news agency said, citing hospital representatives.
About 600 Muscovites had to relocate, housed either by relatives or in city-paid hotels, the agency said.
In total, 31 apartment buildings were left without gas, though city authorities vowed to wrap up the repairs by Tuesday.
Officials agreed that the mass fires were caused by a gas pressure spike at the distribution station, but differed on what caused it.
Biryukov blamed the incident on a malfunctioning vent, while the Investigative Committee, cited by TASS, spoke about gas station employees botching safety procedures.
The city and the Investigative Committee launched separate investigations into the incident. No one has been charged as of Monday.
This is the second major infrastructure incident in Moscow in as many weeks. Last Monday, much of the city was blanketed in acidic smog and reeked of sulfur amid reports of toxic chemicals in the atmosphere.
A handful of industrial facilities in the city's south, including a Gazprom-owned refinery, were named as possible culprits, but all denied involvement. Officials have so far failed to establish what exactly fouled up the city air for hours.
Moscow has seen 19 gas-related incidents since 2000, with a total body count of 44, according to TASS. However, none has been blamed so far on gas infrastructure problems.
