VANCOUVER -- An extensive search for a missing father and son is continuing east of Pemberton, as concerns grow that the pair wasn't equipped to spend multiple days in cold weather.

The Líl̓wat Nation first posted a notice Friday that 48-year-old Peter Oleski and his 21-year-old son, River Leo, were missing. The notice said the two men didn't return home after a mushrooming expedition in the Upper Mackenzie Basin.

On Monday, search and rescue supervisor Paul Berry said the only thing found so far has been water bottles belonging to the men. 

"High-tech technology used over the search area in very quick proximity after they disappeared with no targets so there is a deep concern that they are unable to respond to searchers," Berry said. 

He explained there are 11 search teams from around the province taking part in the large-scale effort. 

Searchers also learned the two men did not have proper clothing for the conditions or food. 

"They were not that well-equipped and basically planning on mushroom picking for the day," said David MacKenzie with Pemberton SAR. 

In a message posted to Facebook Tuesday, Pemberton's mayor says he's grateful to the search and rescue teams that have poured their energy into several days of searching. 

"My heart is heavy with worry and concern for them, their families and the Líl̓wat community," Mayor Mike Richman wrote. 

"Our collective and connected effort gives me the hope that Peter and River will feel and hear our call for them to come home. Líl̓wat, please know you are in my thoughts and I send you strength and love."

Two base camps have been set up for the operation. One is at Pemberton Regional Airport, where crews are leaving by helicopter, and the second is set up along the Mackenzie Basin Forest Service Road, where volunteers are joining members of the Líl̓wat Nation to search the area on foot.

On Monday temperatures in Pemberton are expected to stay around 3 C, with periods of rain.