A man was found dead at the construction scene around Derry Road and Bronte Street, about 50 kilometres outside Toronto. It is reported he was acting as the flagman at the site.
Police are withholding the man's name and age until next of kin are notified.
Derry Road will be closed for several hours during an investigation into the death.
This marks the seventh construction death in Ontario in 2014.
More to come.