The cause of the fire was under investigation, but media reports blamed either an overheated fryer or a faulty air compressor.
``The restaurant will be closed until further notice pending an investigation,'' Hard Rock Cafe spokesman Steve Glum said.
Clouds of smoke wafted through parts of old San Juan, a historic and tourist area in the U.S. territory's capital ringed by 16th-century forts, brightly colored Spanish colonial buildings and cobblestone streets.
Dozens of people from 11 buildings were evacuated. Two people, including one firefighter, were treated for smoke inhalation.
The fire partially collapsed the restaurant's dining room roof and destroyed the kitchen and administrative office, while smoke and water damaged other rooms.
Hard Rock Cafe International Inc., based in Orlando, Fla., operates 110 restaurants in 39 countries.
