HOUSTON -- The lights are back on in downtown Houston after a fire at a power substation left businesses and residences in the dark on Thursday, KPRC Local 2 reported.

CenterPoint Energy officials said a breaker the Gabel substation on Elysian Street near Crawford Street caught fire at about 2:30 a.m.

The cause of the fire is under investigation, company officials said.

Officials said the Gabel substation is as a junction point along the electrical network that connects power plants, high-voltage transmission lines and lower distribution lines.

Officials said about 400 commercial and residential customers were without power for about seven hours. One customer could be an entire high-rise building, officials said.

The outage left many downtown employees waiting to get to work.

"I was just hoping when I got here that everything would be taken care of," credit union employee Tamyra Winters said. "It's not, so I just have to wait and see."

The majority of the commercial customers without power were in the northeast section of downtown, officials said.

Buildings affected by the outage included:

Courthouse District
U.S. Post Office (operating on partial power as of 11 a.m.)
Rice Garage
Sam Houston Hotel
Houston Chronicle
Lancaster Hotel
Civic City Garage
Inn at the Ballpark
Wel-Tec Building
Texas State Hotel
Hogg Building
Fidelity Building
Byrd Loft
Harris County Central Plant