A Calgary alderman says there should be greater vigilance at highrise construction sites after the latest in a string of incidents where objects have come crashing to the ground.

A wrench fell Saturday from the 45th floor of a skyscraper under construction downtown, breaking a window in the city police headquarters.

The incident occurred at the Bow building, located on two blocks of Centre Street and 5th and 6th avenues S.E., around 12 p.m.

Police said no one was hurt when the two-kilogram hand tool bounced off a concrete apron and smashed a window in the police building across the street.

"I think what's happening is because we were experiencing such a huge amount of development that as a result we have seen more incidents because of the fact that there's all of these sites in progress," said Ward 8 Ald. John Mar, who is a member of a committee formed by the city and the Calgary Construction Association to examine safety issues.

The committee was established after Michelle Krsek, 3, was killed last August when she was hit by a piece of metal that blew off the18-storey Le Germain hotel and condo site at 112 Ninth Ave. S.W.

"We know that is largely preventable. And what we need to do is we need to continue to be stressing safety, safety, safety to the workers that are putting it together, to the designers and developers and bystanders," said Mar.

Occupational Health and Safety is investigating Saturday's incident, and could order the construction company to take steps to prevent a recurrence including better protection and training programs for workers.

"There will be two parts to our work. The first part is to determine exactly what happened and the second part is to determine that there are systems in place to ensure that it doesn't happen again," said provincial spokeswoman Janice Schroeder.

With files from The Canadian Press