BRUNSWICK, Maine — A 53-year-old Brunswick man was transported to a Portland hospital with life-threatening injuries after an apparent explosion inside a five-unit Brunswick apartment sparked a two-alarm fire this afternoon.

Brunswick Fire Department Deputy Fire Chief Ken Brillant said crews responding to a report of a fire at approximately 2:30 p.m. found the man outside the building suffering from smoke inhalation and facial burns. He said he did not know how the man got outside.

The fire, at 23 Oak St., was extinguished at 2:55 p.m. The Office of the State Fire Marshal has been called to investigate.

Unconfirmed reports from bystanders indicate an oxygen tank within a residence may have exploded. The man was taken to Maine Medical Center in Portland by Brunswick Rescue.

Brillant said most of the damage was confined to the man’s apartment, although a lower apartment may also have sustained water damage. He said most of the residents of the apartment building will be able to reoccupy their dwelling tonight.