Pershing County deputies say aircraft went back up at about 6:30 a.m. Monday to look for 34-year-old James Glanton, his 25-year-old girlfriend, Christina McIntee, and the four children: a 10-year-old, two 4-year-olds and a 3-year-old. The relationship between the couple and children was unclear.
Officials say the group went to the Seven Troughs area at about noon Sunday in a 2005 Jeep.
Dispatcher Jerry Reid says a search and rescue operation started a little after 8 p.m. and continued through most of the night.
The temperature in the nearby small town of Lovelock dipped to 16 below zero Monday morning.