Police Chief Michael Morrill said two people suffered minor injuries and one person was unaccounted for following the explosion, which happened at about 6:20 a.m. Tuesday in Yarmouth.
John Vincent said he heard the blast and felt the earth shake in his house a few hundred yards away.
"I initially thought something had hit my house, or a small plane had crashed into the woods," he said. He looked out, but couldn't see anything; a neighbor later told him what happened.
Police say the cause of the explosion appeared to be linked to propane.
The condo complex is made up of groupings of modern, upscale attached homes. The explosion disintegrated one unit, turning wallboard into powder and tossing wood into haphazard piles.
Power was cut off to the town.
On Feb. 12, a leak in a propane line caused an explosion to a home in Bath that killed a woman who was inside. It leveled a two-unit apartment building.
The Maine Fuel Board, which regulates propane and natural gas, was investigating that explosion.