DEBKAfile: Two Saudi nationals are under detention on suspicion of involvement in Monday’s Boston Marathon bombings Tuesday which left three dead and 176 injured - 17 critically. One of the Saudis faced questioning  in hospital with burns on his hands and a second was taken into custody at their apartment over “visa problems.” A third Saudi s the object of a wide police FBI hunt. Security was beefed up at Logan international airport Tuesday n case of an attempt by the third wanted third Saudi to flee the country. At Logan airport, a plane has just been grounded over the suspicion that he may be aboard.