Five other workers were injured, one critically, at the site of the 40-plus-story luxury condo tower on Biscayne Bay on Tuesday.

The part that fell was a section workers had been raising to extend the equipment's reach, Miami fire spokesman Ignatius Carroll said. The crane's main vertical section was intact.

The section smashed through the Spanish-tiled roof of the two-storey home, which police spokesman Delrish Moss said had been used in the 1998 comedy film 'There's Something About Mary.'

Emergency workers and dogs found no evidence of trapped victims, but fire officials said rescue efforts were hampered because the crane section remained unstable. Rescue workers were trying to secure a severely damaged wall before re-entering the house to check for anyone inside.

Mr David Martinez, 31, a pipe fitter, was on the fourth floor of the condo tower eating lunch when the crash occurred.

'It was like a small earthquake,' he said. 'We looked outside, and we couldn't even see.' It took several minutes for the dust to clear, Mr Martinez said.

One of those killed died in the house, and the other died at a hospital, police spokesman Delrish Moss said.

Ms Mary Costello, a senior vice president for Bovis Lend Lease Holdings, which was managing the construction, said the accident occurred when a subcontractor tried to raise the crane section and it came loose.

The company is cooperating with investigators, she said.

'Our hearts are heavy at this moment for the two deceased individuals, including one of our own employees and the additional injured workers,' she said in a statement.

The subcontractor, Morrow Equipment, and the tower developer, Royal Palms Communities, did not return phone messages seeking comment.

The US Occupational Safety and Health Administration had two investigators at the site.

Ms Darlene Fossum, an area director for the agency, said Bovis Lend Lease had partnered with OSHA in the past and was considered a company that went 'above and beyond' in terms of safety and health.

Ms Fossum added that OSHA issued five violations against Morrow in a December 1999 incident in Florida, but those mostly involved problems with digging and not cranes. The Salem, Oregon-based company has faced 15 inspections nationwide.

The state of Florida does not license or regulate tower cranes or crane operators, but bills moving through both houses of the Legislature would change that.

In 2006, a fatal crane accident in Miami-Dade County prompted local officials to work with industry leaders on an ordinance that would beef up inspections and safety measures for lifting cranes. The law is to go into effect on Friday.

Tuesday's accident came 10 days after a 20-storey crane toppled at a New York construction site, killing seven people. The crane demolished a four-storey town house and damaged several other buildings.

New York City officials said on Tuesday they have told contractors they cannot raise or lower large cranes at construction sites unless a buildings inspector is there. -- AP