MOSCOW >>  Firefighters extinguished a massive fire aboard a docked Russian nuclear submarine Friday as some crew members remained inside, officials said, giving assurances that there was no radiation leak and the vessel’s nuclear-tipped missiles were not on board.

Military prosecutors have launched an investigation into whether safety regulations were breached. President Dmitry Medvedev summoned top Cabinet officials to report on the situation and demanded punishment for anyone found responsible.

The fire broke out Thursday at an Arctic shipyard outside the northwestern Russian city of Murmansk where the submarine Yekaterinburg was in dry-dock. The blaze, which shot orange flames high into the air through the night, was put out Friday afternoon and firefighters continued to spray the vessel with water to cool it down, Emergency Situations Minister Sergei Shoigu said.

Russian state television earlier showed the rubber-coated hull of the submarine still smoldering, with firefighters gathering around it and some standing on top to douse it with water. Most modern submarines’ outer hulls are covered with rubber to make them less noisy and more difficult for an enemy to detect.

Seven members of the submarine crew were hospitalized after inhaling poisonous carbon monoxide fumes from the fire, Shoigu said.

An unspecified number of crew remained inside the submarine during the fire, Defense Ministry spokesman Col. Igor Konashenkov said in a statement. He insisted there never was any danger of it spreading inside the sub and said the crew reported that conditions on board remained normal.

Konashenkov’s statement left it unclear whether the crew were trapped there or ordered to stay inside.

There has been no radiation leak from the fire, the Defense Ministry and Foreign Ministry said, and Norway’s Radiation Protection Authority across the border reported it has not measured any increased radioactivity.

The governor in Finnmark, Norway’s northeastern province that borders Russia, and the radiation agency complained about the Russian response.

"There have been problems to get clear information from the Russian side," Gunnar Kjoennoey told Norwegian broadcaster NRK. "We have an agreement to exchange information in such cases, but there has been no information from the Russian side so far."

Russia’s military says the blaze started on wooden scaffolding and then engulfed the sub’s outer hull. The vessel’s nuclear reactor had been shut down and its nuclear-tipped missiles and other weapons had been unloaded before dry-dock repairs, it said.

Toxic fumes from the blaze had spread to the town of Roslyakovo where the shipyard is located, but officials said there was no need to evacuate local residents.

The Interfax new agency quoted the former director of the biggest shipyard in the area as saying the fire was probably caused by the failure to take proper safety precautions, such as coating the scaffolding with special sprays to make it fire-resistant.

"It was either lack of professionalism or an attempt to save money that has turned into huge losses," Nikolai Kalistratov said.

The Yekaterinburg is a Delta-IV-class nuclear-powered submarine that normally carries 16 nuclear-tipped intercontinental ballistic missiles. The 166-meter (548-feet) vessel has a displacement of 18,200 tons when submerged.

The chief of the General Staff of the Russian armed forces, Gen. Nikolai Makarov, led a team of senior military officials to Roslyakovo to oversee the emergency response.

The damage from the fire could be so massive that the submarine would need to be scrapped, the Interfax news agency reported Friday. But Deputy Prime Minister Dmitry Rogozin, who is in charge of the nation’s military industries, said that the submarine will rejoin the navy after repairs.

The Russian navy suffered its worst accident in August 2000, when the Kursk nuclear submarine exploded and sank during naval maneuvers, killing all 118 crew members aboard.

A 2008 accident at the Nerpa nuclear-powered submarine killed 20 Russian seamen and injured 21 others when its fire-extinguishing system activated in error and spewed suffocating Freon gas.

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Jan M. Olsen contributed to this report from Copenhagen.