Hydro One says it has grounded all its helicopter crews in the aftermath of a chopper crash that killed four employees in eastern Ontario.
CEO Mayo Schmidt says the fleet will not operate until investigators finish reviewing safety protocols, equipment and mechanics.
He says the review is standard procedure after any serious workplace incident, adding there is no timeline as to when helicopter crews will go back to work.
Schmidt says Hydro One workers across the province are reeling from the deaths of their colleagues.
None of the four workers on board the Aerospatiale AS350-B2 chopper survived after the helicopter went down shortly before noon in Tweed, Ont., on Thursday.
Hydro One is holding candlelight vigils at offices across Ontario Friday to honour the four men.
Schmidt also says most ground crews in the province will be standing down from their jobs until Monday to mourn the loss of their colleagues, but workers will respond to any reports of power outages.
He adds that the company is assisting employees and the families affected by the crash with a wide range of services, including grief counselling and help making funeral arrangements.
The names of those who died have not been released.
The Transportation Safety Board has said its investigators would be looking at a wide range of factors to determine a possible cause of the crash, including pilot records, aircraft maintenance records and aircraft history.
The single-engine AS350 is a utility helicopter often used for corporate purposes and by police.