The border patrol helicopters are still out, searching the desolate desert near the Mexican border.

Patrols ran across the first group of immigrants on Wednesday, exhausted and dehydrated.

The smugglers who took them across the border had abandoned them last Saturday, telling them they were only a couple of miles from a road.

Long trek

In fact the road was more than 80km away, and the Mexicans wandered for five days, in temperatures which reached 46C.

A search began for their companions. Survivors were airlifted to hospital in the town of Yuma.

Dr Shawnna Delsorbo said they were in a very bad state - one was actually dead on arrival.

Captain Cyril Atherton says he believes some members of the group may still be unaccounted for.

"We have a rough estimate of anywhere from 25 to 28 individuals total in the group. We will continue looking and pushing any kind of foot sign out there until we find everyone we can out there," he said.

This is the worst incident of its kind in Arizona.

Local residents say government policy has made the border crossing far more dangerous.

Border patrols concentrate their efforts on the more populated parts of the border, forcing the smugglers and their clients to take the risk of crossing through the desert.