By Ros Krasny and Lauren Keiper
BOSTON (Reuters) - Thousands remained without power in Boston on Wednesday morning after a transformer fire caused a massive blackout on Tuesday night, forcing tourists and Bostonians to flee onto eerily darkened streets beneath thick black smoke.
The three-alarm fire in Boston's congested Back Bay neighborhood cut power to hundreds of residences, businesses and hotels, disrupted public transport and briefly prompted authorities to urge residents to stay indoors because of fears of toxic fumes.
Power was restored to about 10,000 customers overnight, with another 11,000 still in the dark, according to NSTAR, the electric utility.
NSTAR expects full restoration to take into the evening hours. The utility was relying on generators brought in from across New England and New York.
"Our focus right now is getting customers back online," said NSTAR spokesman Michael Durand. "When that's complete, then we'll turn our focus to the cause."
Firefighters on Tuesday evening responded to a fire in a 115,000-volt transformer at an NSTAR substation in a garage close to the Back Bay Hilton, a recently renovated 390-room hotel. The densely populated, upscale neighborhood affected by the fire is usually crowded with locals, business travelers and tourists at shops, bars and restaurants on Newbury and Boylston Streets. Many were out on the streets enjoying unusually mild March weather when the fire broke out.
The Boston fire department cut power to the area as a precaution, plunging the distinctive Back Bay skyline, including the 60-story John Hancock Tower, the city's tallest building, into darkness.
"Thick, black, acrid smoke" poured from the scene of the fire, said fire department spokesman Steve McDonald.
Power outages spread from the Back Bay to the adjacent Theater District, Chinatown, Kenmore Square and the South End.
City officials urged people to take public transit early Wednesday and seek alternate routes around the Back Bay area. Dozens of intersections remained without traffic lights.
Cleanup "has been non-stop since midnight," the fire department said.
(Additional reporting by Scott Eisen; Editing by Daniel Trotta)