ST. PETERSBURG -- A fire in the Admiralty naval academy, one of St. Petersburg's best-known buildings, destroyed about 100 square meters of its top floor, officials said Saturday. No one was injured in the blaze.

Authorities were still investigating what caused the fire in the Admiralty on Friday evening.

A duty officer at the city's fire service said about 100 square meters of the top floor of the academic wing were destroyed. He said the ruined rooms housed sailors' clubs of the Dzerzhinsky Naval College.

It took firefighters eight hours to extinguish the blaze, the duty officer said. Their efforts were slowed by temperatures of minus 30 degrees Celsius, which caused hydrants to freeze.

The Admiralty dates from the early 1700s, when Tsar Peter the Great ordered shipbuilding operations for the nascent navy moved to the city he was constructing as Russia's window to the west. The current building dates from 1825 and has been used primarily as a military school since shipbuilding ended there in the mid-19th century. Its golden spire is a key city landmark.

Several St. Petersburg landmarks, including an 18th-century church and the Moscow Station, have been hit by fires in recent months.