BIRMINGHAM, Ala. — Firefighters were digging through rubble today, searching for two people unaccounted for after an early-morning explosion ripped through a Birmingham apartment building.

Seven others — four children and three adults — were injured in the explosion, shortly before 3 a.m. at the Gate City Apartments in Alabama’s largest city. Two five-bedroom apartments were destroyed.

Survivors crawled through fire and debris to get to the street to safety, but their injuries were mostly scrapes and burns, none life-threatening, Fire Chief C.W. Mardis said.

The fire burned for about two hours and was extinguished by 6:30 a.m., authorities said. Dozens of people were evacuated from nearby buildings and are staying at a shelter.

“Right now we don’t have the exact cause,” Mardis said shortly before dawn, during a brief news conference at the scene. “We do have Alagasco and other utilities on the scene trying to determine what happened.”

Alagasco supplies natural gas to homes and businesses in the Birmingham area.

“Right now we’re in the phase where we’re trying to determine where the two missing people are,” Mardis said. “We also do have the fire under control at this time, but we’re still putting out hot spots.”