Most of a Bethesda high-rise remains without electricity and water after a fire Saturday, meaning hundreds of displaced residents won't be able to return to their apartments for days, authorities said Sunday.

A fire broke out in the building's below-ground electrical room Saturday morning, sending more than a dozen people to the hospital and prompting the evacuation of the 550-unit tower at 5225 Pooks Hill Rd., and displacing as many as 1,500 people. Montgomery County Fire and Rescue crews responded to a call of smoke on the upper floors about 9 a.m. Saturday, officials said.

Fire department spokesman Pete Piringer said Sunday that six people were treated for smoke inhalation, and another dozen were taken to the hospital for other medical reasons — including existing conditions that required them to be under medical care.

An emergency shelter coordinated by the Red Cross and the county hosted up to two dozen people overnight, Piringer said. The rest were assumed to have stayed with family or friends or stayed in hotels, he said.

[Six residents and a firefighter evaluated after blaze at Md. apartment; 1,500 displaced]

Piringer said residents were allowed back into the building — the North Tower of a two-building high-rise complex — to retrieve personal items and medication. An emergency generator was powering elevators and hallway lighting, but was could not power individual apartments, he said. There was no water above the building's seventh floor, he said.

The fire was believed to have been accidental and originated with the power system, though investigators had not specified an exact cause by late Sunday afternoon. The damage was estimated at $1 million, the fire department said.

More than 140 firefighters responded to the scene, first clearing a stairwell of smoke before coordinating an evacuation of hundreds of residents down 18 floors. Crews also swept individual floors and apartment units to make sure everyone inside the building was accounted for.

It's a large building so [it's] logistically very challenging," Piringer said.

The development, Promenade Towers Bethesda, consists of two high-rises. Residents of the South Tower were allowed back in on Saturday, but because the North Tower did not have power or water, occupants could only retrieve their essential belongings and medication — but could not stay overnight.

A call to the Montgomery County Office of Emergency Management and Homeland Security, which took over after the fire department cleared the scene, was not immediately returned.