Police say it’s surprising there were no serious injuries in a multi-vehicle accident Tuesday afternoon on Highway 400.

The accident, in the northbound lanes just north of Highway 88, involved two tractor trailers, three pickup trucks, an SUV, and a mobile home resulted left four people with minor injuries.

Witnesses say it all happened very quickly.

“I saw a transport cut across 3 lanes and that camper just exploded into a million pieces. It was a big explosion, and then all of a sudden I just hit the brakes,” said a witness.

The SUV flipped and one of the tractor trailers went straight through the centre guard rail.

“It could definitely have been more tragic,” said Constable Lisa MacIntyre with the OPP. “When you see the whole seriousness of the collision we're very fortunate they were not serious injuries.”

Only minutes before this crash, police had closed one lane on Highway 400 northbound to respond to another crash along the same stretch of the highway.

“We had a dump truck that went through the guardrail in the right ditch,” said MacIntyre. “So we did have a lane closure. Whether it was in relation to traffic that was slowing down, I don't know at this point.”

The northbound lane of Highway 400 was shut down for hours but was reopened late Tuesday afternoon.

The cause of the crash is still under investigation.