CINCINNATI - A floor collapsed into a V shape yesterday at the construction site of a new casino, sending workers sliding down to the ground and injuring at least a dozen of them.

Authorities said there were no life-threatening injuries in the collapse, which came weeks after a similar accident at a Cleveland casino with the same developer.

The collapse occurred shortly before 8 a.m. as a crew was pouring a section of concrete floor, said Steve Rosenthal of casino co-developer Rock Gaming LLC. Rosenthal told reporters that it was too soon to determine what caused the collapse.

Fire Chief Richard Braun, who was one of the first on the scene after the collapse, said that a beam supporting the floor “sheared away’’ and the floor came down while the workers were on top of it.

“They basically rode the V down,’’ Braun said. No one was underneath the 60-foot-by-60-foot section of floor.

The injured were sent to hospitals with what appeared to be mostly bruises and bumps, and possibly some broken bones, the fire chief said. All workers were accounted for, according to Rosenthal.

Jessie Folmar, a spokeswoman for Cincinnati-based Messer Construction Co., said the company was trying to learn what happened yesterday.

Messer has had a clean safety record with the Occupational Safety and Health Administration since 2006, according to information from the agency’s database. Its last accident in Ohio incident was that year, when it was penalized for four serious violations and paid a penalty of $3,125. One involved a lack of adequate fall protection for workers.

OSHA inspectors, as well as investigators from the state, were looking into the accident.