DETROIT, Jan. 28 (UPI) -- Federal agents Friday tried to find a man who called 911 from metro Detroit and threatened to kill President Bush and the city's mayor. The U.S. Secret Service is investigating the threat, which was determined to have come from Detroit's east side Wednesday night, WDIV-TV, Detroit, reported Friday. Detroit police were sent to Detroit's east side but only found businesses and a cell tower, the station said. Federal agents hoped a recording of the 911 call would help identify the caller, who threatened Bush and Detroit Mayor Kwame Kilpatrick.