Seventeen migrant workers were killed in a fire on Tuesday in a market warehouse on Moscow's outskirts where they had been living, Russian emergency officials and media said.
Most of the victims were from Tajikistan and the others may have also come from ex-Soviet republics, state media said. The pre-dawn blaze highlighted the dangerous conditions many labour migrants endure in Russia.
The space was not meant for people to live in, emergency official Sergei Gorbunov told state-run news agency RIA.
The metal-sided two-storey building was used as a storage warehouse at a construction materials market, said Gorbunov, deputy chief of the Emergency Situations department in Moscow's southwestern district. The victims had been living in makeshift quarters in the rear of the building, he said.
Why people were living there and what relationship they had with the market will be established by the investigation, he added.
Authorities have opened a criminal investigation on suspicion of fatal negligence of fire safety rules.
It was the deadliest fire in the Russian capital since a December 2006 blaze killed 46 patients at a hospital for people with drug dependency problems, Interfax reported.
Millions of migrants from poor former Soviet republics such as Tajikistan, Uzbekistan, Kyrgyzstan and Moldova work on construction sites or do menial jobs in Russia.
Many of them are in Russia illegally, work in or around Moscow and live where they work or in cramped spaces rented from employers.
Money that Tajik migrants send home accounts for nearly 40 percent of the impoverished nation's $6 billion economy.
Death rates from fires are far higher in Russia than in Western nations. In 2010, fires killed nearly 13,000 people in Russia and roughly 3,000 in the United States, whose population is more than twice as large as Russia's 143 million, according to Russian and U.S. government statistics.
(Writing by Steve Gutterman; Editing by Alessandra Rizzo)