ivan watson is in seoul for us. before we get to the escalating tension, what more do we know, if anything, about why this additional american was not allowed to board his flight out of pi i don't thiyongyang? >> reporter: we don't have any charges yet that have been leveled against him. most of the information coming from the swedish embassy in pyongyang because it represents u.s. interests in north korea since there are not direct relations between pyongyang and washington. we do know that he was trying to fly out of the country, after teaching for weeks at this pyongyang university, and if the past track record for americans who have been detained by the north koreans is any indicator, he's in a very serious situation, probably about a half dozen americans over the last five years grabbed by the north koreans usually at the airport when they're on their way out and most of them it has taken weeks, if not months before they are released. two other americans are currently in custody right now.