Search parties continued looking for a couple and four children who disappeared after traveling to the mountains of northwest Nevada to play in the snow and never returned on Monday.

Police in Pershing County told the Associated Press that rescue teams both in the air and on the ground have been sent to look for 34-year-old James Glanton, 25-year-old girlfriend Christina McIntee and four children: a 10-year-old, two 4-year-old kids and a 3-year-old.

Authorities are still not sure how the couple and children are related.

The six reportedly traveled to the Seven Troughs region of the western Pershing County, Nev. mountain range on Sunday, amid unprecedented low temperatures in the area.

National Weather Service Meterologist Mark Deutschendorf told AP that temperatures in the nearby city of Lovelock fell to -16 on Monday morning, intensifying the need for rescue teams to locate the couple and four kids.

Search groups were deployed to the location just after 8 p.m. on Sunday, and went on looking through the evening. The U.S. Navy is still searching for the six, while deputies are considering bringing the Civil Air Patrol for assistance.

The group reportedly drove a silver Jeep with a black top to the mountains, but officials don't know what materials they brought with them or if they had a way to speak with rescuers or local dispatchers.