The fire, which broke out at about 3.00 a.M. Local time in the one-story hospital in the Ramenskoye settlement, was caused by a short circuit, Russian news agency RIA Novosti quoted police officials as saying.
"According to preliminary reports, 38 people died, including two medical personnel," a Health Ministry spokesman, Oleg Salagay, was quoted as saying by the news agency.
"Three people survived - a medical nurse lead two patients out of the burning building," Salagay said, adding that a total of 41 people were believed to be in the one-story building at the time of the fire.
So far 12 bodies had been found in the building that almost completely burned down. The search is hampered by heavy clouds of smoke around the site, it added.