A child is among five people missing near the Goldfields region, with an air search under way on Saturday morning to locate them.
Police believe the group - two men, two women and an eight-year-old boy - were travelling in a green Hyundai Excel sedan from Kalgoorlie to the Tjuntjuntjara Community.
Their vehicle may have become bogged due to recent heavy rainfall in the area, with roads subsequently closed due to flooding and hazardous conditions.
The occupants of the Excel are believed to be Rex Mitchell, 41, Janice Stevens, 43, Bruce Stevens, 24, Shonna Jamieson, 46 and the young boy.
The group departed Kalgoorlie sometime on Tuesday and police are concerned for their welfare as it is unknown if they have food or water.
A search plane departed Kalgoorlie on Saturday morning, with a DFES observer on board to assist the search.
Police have notified surrounding pastoral stations but no land-based search is possible due to bad weather.