MOSCOW (AP) _ A fire broke out in a women's ward of a Moscow drug treatment hospital early Saturday, killing 45 women trapped by barred windows and a locked gate, officials said.

Russia's chief fire inspector, Yuri Nenashev, said he was ``90 percent certain'' that the fire was caused by arson. But Moscow city prosecutor Yuri Syomin said investigators were looking into other possibilities, the ITAR-Tass news agency reported.

The fire erupted in a wooden cabinet in a kitchen at one end of a corridor on the hospital's second floor _ a factor that led to suspicions of arson _ and the only possible exit was blocked by a locked gate, Nenashev said. The barred windows were also locked.

All 45 women were already dead by the time firefighters arrived, said Alexander Chupriyanov, the deputy emergency situations minister.

``Judging by the placement of the bodies, they really tried to get out,'' he said.

About 160 people were evacuated from the five-story Hospital No. 17 in southern Moscow, said Moscow Fire Department spokesman Yevgeny Bobylyov. But he accused hospital workers of not reacting to the fire sooner and evacuating people more quickly.

Most victims died of asphyxiation, while some died of burns, officials said. Ten people were hospitalized for carbon monoxide poisoning, Bobylyov said. Russian news agencies said two hospital staff members were among the dead.

Nenashev said fire inspectors had visited the hospital twice earlier this year and recommended temporarily closing the facility because of fire safety violations.

``Unfortunately this decision was not adopted,'' he told reporters at the scene.

Russia records about 18,000 fire deaths a year _ roughly 10 times the rate in the United States. Experts say fire fatalities have soared since the collapse of the Soviet Union, in part because of lower public vigilance and a disregard for safety standards.

A few ambulances were lined up early Saturday outside the hospital, a nondescript, brick building in a residential neighborhood. Reporters were kept well away from the building, which did not have any obvious signs of fire or smoke damage on its facade.

A van from the city's psychological health service pulled up outside the hospital and a few people went inside, presumably to provide counseling for relatives of the victims. The relatives were brought into the staff entrance to the hospital, well away from reporters.

Bobylyov criticized hospital officials for not calling the fire department to report the blaze sooner. He said the fire was extinguished within an hour of the first call for help.

``Secondly, the hospital personnel worked very badly, they did not take steps to evacuate people in the early stages of the fire,'' he said.

The ITAR-Tass news agency said the fire was confined to a small part of the building, but there were heavy concentrations of smoke. Ekho Moskvy radio said that burning plastic wall coverings had worsened the heavy, toxic smoke.

It was the worst fire in Moscow in three years. In November 2003, a pre-dawn fire swept though a dormitory for foreign students who had been quarantined for medical checks, killing 36 and injuring nearly 200. Many were trapped behind permanently locked exits, causing some to leap from the five-story building.

A January fire in Moscow's main oncological hospital caused the evacuation of hundreds of patients but did not result in deaths or injuries. An October 2005 fire at a home for the mentally ill outside the capital killed seven patients, and a fire in a Moscow city hospital the following month killed four.

A fire in a school in the southern region of Dagestan killed 28 children in April 2003, the same week that 22 students burned to death in a wooden schoolhouse in Siberia.