The officials who described what was written on the mirror spoke on condition of anonymity because the investigation was ongoing. Earlier the Transportation Security Administration had said only that a threatening message was written on a bathroom mirror, but gave no details of the message.
FBI agents, Greensboro's police bomb squad, and bomb-sniffing dogs owned by the Piedmont Triad International Airport Authority swept through the plane and its cargo and found no explosives, airport executive director Ted Johnson said. Every passenger was questioned by the FBI, Johnson said.
"Somebody did it but we've got to draw the right clues to the right person," Johnson said.
Amy Thoreson, an FBI spokeswoman in Charlotte, said agents continued their investigation and had no immediate plans to file criminal charges. Agents released the jet back to the airline.
Flight 3006, operated by regional carrier ExpressJet for Continental Airlines Inc., was headed for Dulles International Airport in Virginia when it was directed to land at the airport near Greensboro "out of an abundance of caution," the TSA said.
The plane was met by law enforcement officers after taxiing to a remote area of the airfield.
The Embraer 145 regional jet carried 45 passengers and three crew members, Continental and ExpressJet said. The plane landed without incident, the airlines and Federal Aviation Administration spokeswoman Arlene Salac said.
"Continental and ExpressJet are cooperating with local authorities," Continental spokeswoman Christen David said.