The Food and Agricultural Organization says North Korea knew of the bird flu outbreak a month before its official announcement of the problem.

Hans Wagner, a senior animal health officer of the U-N affiliate, also said Friday that although no additional or human infections have been reported, it is hard to rule out the possibility of further danger.

In an interview with Radio Free Asia, he said the North culled 210 thousand out of one million chickens in three affected farms, and injected its own vaccines on remaining chickens.