Investigators said the two might have simply left and had not called the authorities.

Investigators have received about 10 calls a day since the first billboard appeared in February.

Kenyan investigators called on the public again today to report any suspicious behavior.

The investigators are calling people they have identified on the tapes and urging them to help.

The search is in its early stages, what investigators call "tag and bag."

At times, the investigators would stop, call New York, and then start questioning him again, he said.

Investigators called it one of the worst cases of child sexual abuse they had ever seen.

Intelligence officials have said in the past that some terrorist groups were using the method, which investigators call a "virtual dead drop."

Investigators on the list should contact the facility by e-mail at mpr.assistance@nara.gov or call 314-801-0775 in advance to request records.