MOSCOW, Russia (CNN) -- A series of powerful blasts ignited a fire Friday at a Russian army munitions depot in the outskirts of Ulyanovsk, a city about 900 kilometers (560 miles) east of Moscow, Russian media reported.
Russian state television showed a series of massive explosions resembling fireworks that, it said, went off about every 30 seconds and could be seen and heard as far as 15 kilometers (over 9 miles) from the scene.
Several hours after the first explosion, the governor of the Ulyanovsk region, Sergey Morozov, said in an interview with Russian Channel One TV that the fire had been largely contained, and fire brigades and special rescue teams had managed to keep the flames away from most of the facilities in the ammunition depot.
He said the depot is very large, with "several thousand rail cars" of munitions.
On its Web site, the Russian Defense Ministry said the initial explosion took place around 4 p.m. (8 a.m. ET) "apparently during the disposal of ammunition" at one of the army's arsenals. "The explosion in one of its workshops led to a fire which spread onto adjacent buildings of the military units," the statement said. "The surrounding area is cordoned off. Fifteen fire brigades ... are trying to localize the fire."
In a later statement to Russian news agencies, the Defense Ministry said two servicemen were killed in the fire. But the ministry wouldn't speak to CNN on the phone to elaborate.
The governor's press office told CNN that 43 Russian army servicemen who were at the munitions depot at the time of the explosion were rescued after the fire was contained.
"They were ushered from the bomb shelter of the depot where they were hiding," a press officer said in a brief phone interview. "They are those people who the governor earlier believed to be missing".
In the first hours following the explosion Morozov told Russian TV that 35 people were and "hopes were slim" on finding any of them alive.
The governor's office said it didn't have any casualty figures.
Morozov earlier had said 20 people had sought medical help and 10 of them had been hospitalized. Russian TV, citing sources at the Emergency Situations Ministry, said 11 people had been reported injured.
Russian news agency Interfax reported that Prime Minister Vladimir Putin told the Health and Social Development Ministry "to organize high-standard and urgent medical assistance to all those injured."
He also ordered the Emergency Situations Ministry "to take all necessary measures" in helping regional authorities evacuate residents of the area, spokesman Dmitry Peskov said, according to Interfax.
Morozov said that 3,000 residents had been evacuated from buildings surrounding the military depot.
In a Russian TV interview, he said the explosion was a result of a "breach of a technological process during the disposal of ammunition."
He said the situation was gradually getting under control. "There are considerably fewer explosions and considerably less fire now, but this doesn't mean it's all over. We'll be fighting the fire at least until tomorrow morning," the governor said.
Also earlier, Defense Ministry spokesman Col. Alexei Kuznetsov told Interfax that the army facility stored only "conventional and non-chemical ammunition." He also excluded any possibility that the explosion could have been deliberate.
The Investigative Committee of the Russian Prosecutor's Office told CNN that it had opened a criminal case into the explosion on two charges -- "negligence" and "mishandling of weapons and other dangerous subjects which resulted in the accidental death of two and more people."
Russian TV said there was no threat of air or water contamination in the area resulting from the accident.