An under-construction tunnel in northern Uttarakhand collapsed early on Sunday morning, trapping 40 workers in it and kicking off a laborious rescue operation spilling over to a second day. The workers are labourers hailing from Bihar, Jharkhand, Uttar Pradesh, West Bengal, Odisha, Uttarakhand and Himachal Pradesh, as per the District Emergency Operation Centre. They are safe and have been given food, water and oxygen, as per the latest update from Chief Minister Pushkar Singh Dhami. "Communication has been established with them. All of them are safe and I assure all the family members of the trapped people that they will be soon rescued from the tunnel.Teams are present on the spot and rescue work is underway." CM Dhami said in a press conference. As the rescue operations continue, here's what we know of the situation.