At least 50 people displaced by a three-alarm fire and subsequent gas line break in San Francisco's Tenderloin neighborhood Friday have sought assistance so far at an evacuation center, according to the American Red Cross.

The fire in a five-story, 44-unit apartment building at 540 Leavenworth St. broke out at around 10 a.m., according to San Francisco fire officials.

At least 29 families, including 41 adults, 10 children and nine pets, have requested help so far from the Red Cross evacuation center, which has been opened at The Hamiltons at 631 O'Farrell St., according to Red Cross spokeswoman Cynthia Shaw.

More residents are still expected to arrive home from work and report to the evacuation center, and Red Cross officials are considering opening a shelter for the night to handle the large volume of people, Shaw said.

"Any resident who needs housing or who has not yet registered with us should check in at the evacuation center or call us at (888) 4BAY-HELP," Shaw said.

The fire was contained just after 11 a.m., and only damaged around 10 units, according to San Francisco fire spokeswoman Mindy Talmadge.

However, the entire building was shut down after a broken gas line was discovered, displacing all residents.

One woman was taken to the hospital for treatment for non life-threatening injuries due to smoke inhalation, and another was rescued from her apartment, along with her cat, Talmadge said.

While early reports indicated the fire started in a lightwell, Talmadge said that remains under investigation.