OAKLAND (CBS SF) — Two men were killed and dozens were displaced by a three-alarm fire in Oakland early Saturday morning at a former armory building converted into apartments, a fire official said.

Fire crews responded to a report of a smoke detector that went off in the 600 block of 24th Street shortly before 3 a.m., Battalion Chief Geoff Hunter said.

A crew arrived to investigate the report and found smoke coming from a second-floor apartment unit, prompting a first-alarm response at about 3:20 a.m., Hunter said.

As crews arrived on scene the blaze was upgraded to a second alarm then third alarm, he said.

The fire started in a large two-story apartment building containing six units and spread to a rear, adjoining building with 35 units, which were not all occupied, according to Hunter.

Both buildings were originally one structure that served as an armory, but have since been split into two, Hunter said.

The blaze quickly spread through a roof shared by both buildings, he said.

The blaze was under control at about 4:10 a.m., Hunter said.

All the occupants from both buildings were able to evacuate on their own except for two people who died inside the unit where the fire started, he said.

The deceased were a 35-year-old man and a 28-year-old man, according to Hunter.

Oakland police and fire investigators remain at the scene this morning, he said.

About 30 people were displaced by the fire and were receiving assistance by the American Red Cross, who opened an evacuation center at its office located at 3901 Broadway.

No other injuries were reported.

The cause of the fire is under investigation.

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