Eight people were found suffering from heat exhaustion and dehydration inside the back of a U-Haul truck in a parking lot northwest of Tucson Sunday afternoon.

Two of the patients are in critical condition, one was in serious condition and five were in stable condition, said Patrick Calhoun a spokesman for the Avra Valley Fire District.

The truck was parked at a Shell gas station parking lot at 16543 E. Camino Adelante, near Picacho Peak, Calhoun said.

The group of suspected illegal immigrants was found inside the truck after a person called 911 to report seeing several people stagger out of the vehicle, said Tim Gaffney, a spokesman for the Pinal County Sheriff's Office.

Several people were seen fleeing from the scene on foot, he said. Between three and six people believed to be in the truck were unaccounted for, Calhoun said.

When emergency crews arrived on scene one man was in cardiac arrest, Calhoun said.

The patients are mostly adult men and women and one 16-year-old boy.

Initial reports indicated the group was traveling from Douglas to Phoenix and the patients had been in the U-Haul for three to four hours, Calhoun said.