The deaths were due to carbon monoxide poisoning, according to the city's emergency situations department.
"In the course of reconnaissance and extinguishing the fire, 13 dead were initially discovered, their identities are being established," the department said in a statement.
The fire started in the basement of a three-story building housing 72 hostel guests, early Thursday morning. Fifty-nine people managed to escape safely.
Authorities are investigating the cause of the fire.
