ST. CATHARINES, Ont. - A major highway through southern Ontario remained closed late Tuesday several hours after a transport truck hauling a toxic chemical rolled over and forced an evacuation and a shelter-in-place order for surrounding homes and businesses.

The City of St. Catharines said just before 1 a.m. that the shelter-in-place order had been lifted.

Ontario Provincial Police say the crash happened at about 3:20 p.m. when the truck rolled onto a concrete highway divider near St. Catharines.

Sgt. Kerry Schmidt says the truck was hauling phosphine, a flammable and toxic gas.

Niagara EMS Chief Kevin Smith said a shelter-in-place radius around the crash site had been expanded from 1.2 kilometres to two kilometres during the evening as a precaution in case of any leakage from the truck.

Residents were asked to keep their windows and chimneys closed and their air conditioners turned off.

Residents who had evacuated the area as a precaution were being asked to stay away from their homes for the night. A shelter has been set up at the Seymour-Hannah Sports and Entertainment Centre for displaced residents who need it.

No injuries were reported.

The highway was closed in both directions between Ontario Street and Highway 406. The city said it was expected to open at about 3 a.m.

GO Transit said its buses were experiencing delays of up to an hour because of detours around the crash site and expected the delays to continue into Wednesday morning.