The search for a missing five-year-old boy in the Crowsnest Pass area has stretched into its third day, as dozens of crews continue to check the rugged terrain in the hopes of bringing him home safely.Darius Macdougall was last seen on Sunday morning walking with his siblings near Island Lake Campground, about four kilometres south of Crowsnest Pass and roughly 250 kilometres south of Calgary.When the children returned to their campsite, Darius was no longer with them.His family, who lives in the Fort Macleod and Lethbridge areas, immediately contacted police.The search effort has since expanded to include more than 80 ground search and rescue personnel from Alberta and British Columbia.Helicopters, drones equipped with thermal imaging, search dogs, underwater specialists, and swift water rescue teams have all been deployed. RCMP officers have also patrolled nearby roads with emergency lights, hoping to spot the boy.Authorities say Darius has autism, which can make it difficult for him to respond to searchers..UPDATED: Massive search launched after five-year-old boy goes missing near Crowsnest Pass.RCMP Cpl. Gina Slaney said crews worked through the night but were unable to locate him.Police have released a photo and description: Darius is four feet tall, with short brown hair, and was last seen wearing a blue-grey hoodie and sweatpants.Adam Kennedy with Alberta Search & Rescue emphasized that every possible tool is in use.“There are no available resources that have not been deployed here,” he said at a press conference on Tuesday.He noted the area’s challenging geography. “The terrain here ranges from flat ground to steep cliffs, which pose risks to both searchers and the missing child.”Investigators are also interviewing family members who were with Darius when he was last seen. “We investigate all avenues when something like this happens,” Slaney said.“Nothing is too small. We're looking at everything.”Search conditions have been complicated by cold overnight temperatures, which have dropped to between three and six degrees Celsius, raising concerns about exposure.Still, Kennedy said crews remain determined. “There is no talk on the ground of anything other than a positive outcome.”“We’re always going to carry on that hope until the hope is no longer there,” Slaney added, saying no foul play is suspected at this time.