Transports Québec said the sinkhole is about 30 metres deep and 10 metres wide.
It was formed over a culvert. Transports Québec told CBC News recent heavy rains and the Canada Day storm may have contributed to its formation.
At 12 p.m. Wednesday there were about 20 cars backed up in each direction as a result.
Motorists are being advised to use Highway 105 as a detour, or to take the Quyon ferry.