NEW DELHI — Three cranes crashed Monday while trying to lift a steel girder that fell at a New Delhi metro rail construction site, a new setback for the landmark project a day after another accident killed six people there.

Six people sustained minor injuries in Monday's accident, Delhi Metro spokesman Anuj Dayal said.

Four truck-mounted cranes lifted the massive orange girder off the ground when one sustained a mechanical failure in its boom — the long arm used to lift weight, Dayal said.

The sudden shift of extra load caused the booms of two cranes to snap while the third crane toppled over, Dayal said. "It was a very tricky, very difficult and dangerous operation because the space was limited," he told reporters.

Live television coverage showed two of the booms shearing off the multi-wheeled trucks. The third crane keeled over and ended up in a vertical position with its underbelly in the air.

Parts of the truck could be seen falling off the upended machine. People ran helter-skelter.

The accident happened on the southern line being constructed for the New Delhi Metro system, which already has three operational lines.

The metro is the pride of the city of 14 million, where commuters were long forced to rely on rickshaws, motorcycles or smoke-belching buses.

Sunday's accident occurred on a particularly tricky section, where a metal cantilever was being raised to lift a 300-ton prefabricated concrete segment of a bridge, Delhi Metro Rail Corp. chief E. Sreedharan told reporters.

The entire structure tumbled down in a V-shaped pile, crushing workers underneath. Six people were killed and 13 injured.