An airport official says a Lufthansa passenger jet headed for Germany has been forced to return to the Czech capital after smoke was detected onboard. Eva Krejci, spokeswoman for Prague's Ruzyne International Airport, says the pilots of the Airbus A321 bound for Frankfurt requested an emergency landing shortly after takeoff Saturday morning, according to a report of the Associated Press. Krejci says firefighters were present to help the plane land safely, and none of the 120 passengers onboard were injured. It was not immediately clear what caused the problem.