The search for two workers who were swept into a Quebec quarry by a landslide has been suspended until Wednesday morning.

Rescue crews tried to dig through the caved-in gravel pit in L’Epiphanie, northeast of Montreal, for hours but had to call off the search late Tuesday because of unsafe conditions.

The workers, a man and a woman, have been missing since their vehicles plunged into the deep hole. One excavator and two loading trucks were on the site, operated by Maskimo Construction Inc., when the landslide occurred.

A third worker was rescued after the quarry collapsed. He suffered frostbite and some injuries and was lifted out of the quarry by a provincial police helicopter. 

The helicopter then lowered rescue workers and a sniffer dog into the pit, but they were struggling to dig through the gravel. The crew managed to reach one of the trucks, which was partially buried in the gravel, but found no one inside the cab.

Sgt. Benoit Richard of the Surete du Quebec said the rescue effort will continue Wednesday morning, when heavy equipment can be brought to the site to dig through the hardened mixture of gravel and mud.

The rescue mission will be turned over to the municipality and the local fire department, but Surete de Quebec will continue to assist, he said.

Earlier Tuesday, Richard said the terrain is unstable, making it a “delicate” rescue operation.

Authorities are also worried that forecasted freezing rain will prevent the helicopter from assisting the search on Wednesday.

A camera with a heat sensor was also being used in the rescue efforts. 

Police said the gravel pit could be up to 100 metres deep. A geologist said a layer of clay covers the rock in the area and hypothesized that excavation work may have put too much pressure on the soil, triggering the landslide.

Many workers gathered on the site Tuesday, hoping to hear good news. One of them said the group is “like family.” 

“I am still in shock,” said the town’s mayor, Denis Levesque. “It's impossible to comprehend.”

With a report from CTV’s Montreal Bureau Chief Genevieve Beauchemin and CTV Montreal