Quebec union leaders are raising questions about the safety of workers at the CHUM superhospital construction sites.

FTQ-Construction, a wing of one of Quebec's largest union federations, said a worker at the research centre site was struck in the head by a piece of falling ice on Jan. 12.

He remains in hospital and is reportedly in critical condition.

The incident is the latest in a string of accidents at the French-language superhospital construction sites in recent months. There have been at least three incidents at the research centre site south of Viger Street, and one at the hospital site north of Viger.

Last August, a large metal construction beam struck a taxi with two passengers inside which was passing the research centre. The impact smashed the cab's rear window. Earlier that month, a crane operating in the hospital site fell over, blocking part of Saint-Denis Street.

In November, pieces of concrete and other debris fell from an upper floor of the research site on to Viger, damaging several cars.

There were no injuries caused by any of those incidents.

Quebec's workplace health and safety board is now conducting regular inspections at the research site. Entrances to the site have been covered to protect workers from falling ice since the latest accident.

The FTQ said it can no longer tolerate its workers being put in danger on work sites and is calling on the province to revise worker safety legislation.