Thirty-five people were found hiding in the back of the truck behind pallets of green bell peppers, and two others were found hiding nearby, The Arizona Republic reported. They were turned over to Immigration and Customs Enforcement officers.
It was believed at least four others escaped, the newspaper said. The truck was found in the town of Tolleson in Maricopa County.
Tolleson police Sgt. Lisa Mendoza said the immigrants reported they were headed to a drop-house, but police were unable to determine its location. Mendoza said authorities would pursue charges against the smugglers if they can find them.