Detroit ( CNN ) -- Metal detectors belonging to the Secret Service that were on a stolen rental truck have been recovered , a law enforcement source said Monday . The metal detectors , which were to have been used at a campaign event for Vice President Joe Biden , were found at an abandoned house in Detroit and in the U-Haul , left near Henry Ford Hospital , the source said . Authorities want to question a man in connection with the theft of the U-Haul , found a day after it disappeared from its spot at the Westin Book Cadillac on Sunday . Surveillance photos from security cameras at the hotel show a man in a green T-shirt and dark shorts near the truck before it was taken . The stolen truck was found Monday , Secret Service spokesman Ed Donovan said . The law enforcement official , who did not speak for attribution , said there were no weapons inside the vehicle . Biden spoke at a downtown rally organized by the Michigan AFL-CIO . CNN 's Carol Cratty and Jonathan Helman contributed to this report .
NEW : Metal detectors were found in an abandoned house , inside truck , source says . NEW : Authorities want to question a man seen on surveillance video . The rental truck was stolen from a Detroit hotel , found near hospital . Vice President Joe Biden spoke at union rally .