( CNN ) -- At least three people were killed Sunday when a passenger train derailed near Toronto , Canadian officials said . All three people were employees of Via Rail Canada , Michelle Lamarche , a spokeswoman for the railway , said , calling it a `` very sad day for Via . '' At least 45 passengers were injured , three severely , according to John Marginson , chief operating officer of Via . The derailment occurred around 3:30 p.m. in Burlington , about 40 miles southwest of Toronto , Lamarche said . The train , carrying 75 passengers , was traveling from Niagara Falls to Toronto , according to Lamarche . An investigation into the cause of the wreck is under way .
NEW : 45 passengers are injured , rail line official says . Those killed were employees of Via Rail Canada . The train was carrying 75 passengers .