The United States says it is trying to confirm a report that North Korea has detained a second American in addition to a U.S. activist that was apprehended last month for crossing illegally into the communist state.

State Department spokesman Philip Crowley told reporters that the matter is obviously something the U.S. takes seriously and that Washington is attempting to obtain more information on the matter.

Crowley said that although the United States has no confirmation of the report, it is currently operating on the assumption that it's entirely possible that a second American citizen has been detained in North Korea in addition to the activist Robert Park.

Earlier on Thursday, the North's state-run Korean Central News Agency said a U.S. citizen had crossed the North Korea-China border on Monday and is being detained for questioning.