A truck rollover prompted an evacuation for 3,500 households and closed a section of the Queen Elizabeth Way in both directions during the 12 hour long cleanup.

The transport truck was carrying phosphine, a flammable and toxic gas substance that is dangerous when inhaled, when it rolled onto a guardrail on the QEW just west of Martindale Rd. at 3:15 p.m. on Tuesday.

“The substance has been contained within the truck and it is not airborne,” said Niagara Regional police Const. Phil Gavin while cleanup crews were on scene.

Scientists came to the site of the crash and determined there was no leakage from the 45 cylinders carrying the substance, said St. Catharines fire chief Dave Wood.

The QEW was closed in both directions between Ontario St. and Highway 406, but opened before 3:30 a.m. Wednesday morning. All lanes of the QEW are open again except for the Fort Erie bound left lane.

Residents within a 1.5 km radius of the crash were evacuated, while those surrounding the area were asked to shelter in place, meaning they should close windows and doors and stay inside, said Wood. Businesses, including a Family and Children’s Services building, were also evacuated. These precautions were lifted around 1 a.m. ahead of the QEW opening again.

Ontario Provincial Police Sgt. Kerry Schmidt said it was a “mechanical issue” that caused the truck to rollover but the OPP are still investigating.

No other vehicles were involved in the rollover and no injuries have been reported.

Corey Beazer drove by the truck just after the incident happened.

“A police car whipped by (and) five minutes of traffic later I drove by the accident,” he said. “I thought I could see someone moving in the truck.”

Wood emphasized the importance of households having a safety kit prepared in case of emergency, as well as an evacuation plan.