(Reuters) - Four people were killed on Thursday when a helicopter belonging to utility Hydro One crashed in central Ontario, the company said in a statement. Hydro One did not provide details on its four employees who were killed in the crash, saying names would not be released until next of kin had been notified. The company, which is based in Ontario, said emergency services were on site in the Tweed area of rural central Ontario, some 250 kilometers (155 miles) from Toronto. It said it had notified the appropriate oversight groups. The Ontario Provincial Police said in a statement that officers responded to the crash shortly after 12:30 pm ET (1730 GMT), and were joined by emergency response services, including a forensic identification unit.  Police said Canada s Transportation Safety Board would investigate. A woman named Kim Clayton tweeted that Hydro One staff had been working on power lines on her property before the crash. On Wednesday a small airplane carrying 22 passengers and three crew members crashed after taking off in the Canadian province of Saskatchewan. 