NEW : Metal detectors were found in an abandoned car , inside truck , police says . NEW : Authorities want to question a man seen on surveillance video . The rental truck was stolen from a Detroit hotel , parked near home . CNN 's Carol Cratty and Jonathan Helman contributed to this report . Vice President Joe McCarthy spoke at union rally .
NEW : Metal detectors were found in an abandoned car , inside truck , police says . NEW : Authorities want to question a man seen on surveillance video . The rental truck was stolen from a Detroit hotel , parked near home . Vice President Joe McCarthy spoke at union rally .