A fire at the Diego Hair Salon in the Cambridge Galleria Mall last night forced police officers and firefighters to block off JFK Street and evacuate patrons.

The fire, which did not directly cause any injuries, broke out around 7:30 p.m. at 57 JFK St.

The Cambridge Police Department closed JFK Street from Memorial Drive to Mount Auburn Street for about an hour while the authorities worked on the problem.

Firefighters on the scene said that a dryer in the back of the salon caused the fire. The exact cause remains undetermined.

With the last three customers on their way out, Brenda I. Dalli, a hairdresser at Diego, said she discovered the fire.

She said she attempted to put it out using a nearby fire extinguisher while another hairdresser phoned 911.

After closing off the street to prevent the fire from spreading, police officers and firefighters asked the public to evacuate the Cambridge Galleria due to the "serious smoke condition," said one firefighter who responded to the call.

Moviegoers at the Sony Janus Theatre who were waiting for the start of the 8 p.m. showing of Boogie Nights were forced to leave the building.

A representative of the Cambridge Fire Department said officials forced the evacuation because the fire was located directly above the theater.

The Shilla Sushi Restaurant was not in a similar condition of vulnerability, and was the only establishment in the complex not told to evacuate.

No one sustained injuries due to the fire or to smoke inhalation.

But one woman twisted her ankle as she attempted to exit the building, according to a firefighter on the scene. An ambulance took her to a nearby hospital.

By 8:15 p.m., the authorities at the scene allowed patrons to reenter the Galleria. Stores resumed business, and Boogie Nights began to flash upon the screen.

According to Michelle G. Pareira, a Diego hairdresser, the incident was only a "small fire."

Before reentering the salon, she said she did not expect to find extensive damage.

This is the second fire to break out in the Galleria complex within the last month.

A fire caused by blocked ducts signed the Bombay Club restaurant at the end of January.