SAN FRANCISCO (CBS SF) — An early morning fire displaced seven people and damaged a four-story apartment building in San Francisco’s Twin Peaks neighborhood Thursday, fire officials said.

Firefighters responded to the one-alarm blaze at about 2:10 a.m. at Glendale and Market streets.

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Crews were able to extinguish the fire within about an hour, according to fire officials.

One person suffered injuries not considered life-threatening and they were taken to a hospital.

Residents on the first and second floor were able to return to their units, but the third floor is without power and a unit on the fourth floor sustained extensive damage, fire officials said.

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In all, an estimated 21 people were affected by the blaze.

The American Red Cross and city departments are assisting the affected residents. A resident who uses a wheelchair was able to stay with a neighbor and is contacting On Lok Lifeways, which provide services for senior citizens.

Fire investigators are looking into what caused the blaze.

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