William F. O’Connell was inside the Dorchester home where he has lived for the past 81 years when he heard a “boom” along with a ringing telephone around 10 a.m. Tuesday. It was his daughter calling to report she saw a television broadcast about a mobile crane tipping over at a nearby construction site.

“And I said, ‘Theresa, I just seen it,’” O’Connell, 98, said.

The “boom” occurred as a truck-mounted crane collapsed on its right side at the construction site at the intersection of East Cottage Street and Dorchester Avenue, where Boston firefighters arrived to find just one of its 18 wheels in contact with the ground.

The operator of the truck was able to get out and was not injured, said firefighter Brian Alkins, a department spokesman. Workers were inside the construction site, but no one was injured, he said.

East Cottage Street between Dorchester Avenue and Pleasant Street was closed Tuesday afternoon but was reopened around 6:45 p.m.

Around 3:30 p.m., three cranes slowly began lifting the fallen crane from the structure.

The crane was back on the ground around 5:30 p.m. An arm that was extended onto the construction site, was brought down a short time later.

The Occupational Safety and Health Administration, the federal workplace safety agency, and city inspectors are conducting investigations, Alkins said.

Boston Fire Deputy Chief Michael Hocking said firefighters from the specially trained Technical Rescue Unit were among the first responders; they were told that a crane had collapsed into the building. When they arrived, however, he said it was clear the workers were out safely and the driver was unharmed.

“Now there is no danger to anybody specifically. It’s going to be an extended period of time to get the crane removed,” he said. “There were some workers moving some wooden trusses from the sidewalk into the structure. A crane was swinging in and the crane collapsed.”

A tractor-trailer from the Shaughnessy Crane Service arrived on scene shortly after noon, apparently to help in righting and removing the collapsed crane.

The cause of the tip-over was not immediately known.

Hocking said the department “brought in some experts. We brought in OSHA. They’ll get to the bottom of that. It’ll take a little while but they’ll figure it out,” he said.

Yad Malhi said he saw it happen. Malhi said he had arrived at the site with a load of pre-built trusses. He was standing across the street watching as the crane operator removed them from the truck and transferred them onto the job site itself.

”At first, the crane operator was lowering the trusses slowly and then it went down fast,” he said. ”The machine works on the gravity rule. If you’re too much off the balance, it’s going to go down.”

The crane was deployed at the construction of a five-story building that is part of a mixed-use development expected to generate 38 residential units, 26 parking spaces, and a restaurant space on the ground level, according to the Boston Planning and Development Agency postings.

O’Connell literally had a front row seat to the recovery effort.

He brought a folding chair and a battery-powered radio out to his porch so he could watch the scene unfold throughout the morning and afternoon. He tuned the radio to an oldies music station and tapped his foot as he watched three cranes drive onto the scene to right the fallen vehicle.

“There it goes,” O’Connell said as he watched one of the assisting cranes extend all the way in preparation to lift the vehicle.

Due to incorrect information provided to the Globe, an earlier version of this story had the incorrect street location for this incident.

John R. Ellement of the Globe Staff contributed to this report.

Bailey Allen can be reached at bailey.allen@globe.com. Follow her on Twitter @baileyaallen.

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