HOUSTON - A fire broke out at an underground parking garage of a 50-story skyscraper in the US city of Dallas Thursday, killing three people and forcing the evacuation of thousands of office workers, local media reported.

The fire erupted Thursday morning at Thanksgiving Tower's parking garage in downtown Dallas, according to the Dallas Morning News. The fire, believed to be caused by an electrical failure or a car fire, prompted the evacuation of around 2,800 people from the building.

Local TV footage showed swarms of office workers streaming out of the high-rise and smoke billowing out of the driveway that leads to the underground garage.

When firefighters rushed to the location of the fire, they found three construction workers dead at the basement of the skyscraper. The victims were working in the thermal storage tank that is part of the heating, ventilating and air conditioning unit beneath the building.

Three other people were sent to hospitals for treatment. Their conditions were believed to be fair.

The fire, which also temporarily shut down several streets around the building, was extinguished within an hour.

It is not immediately clear how exactly the fire started. The 32-year-old skyscraper is reportedly in the midst of an 18-million-US-dollar renovation.