Moscow (CNN) -- Russia's president on Friday ordered an investigation and the repair of a nuclear submarine that caught fire while docked along the Barents Sea, according to state media.
Nine people were injured battling the blaze in and around the nuclear vessel Yekaterinburg.
A spokesman for the military prosecutor's office for the Northern Fleet, Alexander Grigoryev, told the official Itar-Tass news agency that seven were still being treated in a hospital for carbon monoxide poisoning from the scene of the fire. Two others have been discharged from a hospital, reported RIA Novosti, another state news agency.
On Friday, Russian President Dmitry Medvedev called for an investigation into the incident and said "all necessary measures" should be taken to restore the submarine, according to RIA Novosti, citing a press release from the president's office.
Flames spread to the submarine Thursday afternoon after material caught fire at a dock in Roslyakovo, which is in the Murmansk region in northwest Russia, Itar-Tass reported. The Yekaterinburg was undergoing maintenance at the time.
Capt. Vadim Sega, a spokesman for Russia's Northern Fleet, said the fire never penetrated the vessel's hull and thus did not spread inside the vessel.
"There is no possibility of fire burning through the hull, and no threat to on-board equipment," Sega said Thursday, according to RIA Novosti.
Still, it took nine hours for crews -- at one point about 100-people strong, using roughly 40 pieces of firefighting equipment -- to subdue the blaze, RIA Novosti reported. Russia's Emergencies Minister Sergei Shoigu said Friday that the fire was finally put out.
The submarine's nuclear reactor had been shut down when it was docked for its scheduled maintenance, Russia's foreign ministry said Friday in a statement. It also noted that measurements of background radiation in the area "remain normal."
"There is no threat of radioactive contamination," the foreign ministry said.
Some of the Yekaterinburg's crew remained on board the vessel Friday for "close monitoring of the situation," according to the foreign ministry.
One of seven Delta-IV class submarines in operation, the Yekaterinburg carries 16 ballistic missiles. According to the military research website RusNavy.com, the vessel was launched in September 1984, has two nuclear reactors and can carry a 140-person crew.
CNN's Alla Eshchenko contributed to this report.