The Australian reports:
US intelligence has detected an explosion of less than one kilotonne in magnitude in North Korea but has not been able to determine whether it was nuclear or not, a senior intelligence official said.
The official, who asked not to be identified, said that first-time nuclear tests historically have been in the several kilotonne range.
“We are aware that there was a sub-kilotonne explosion in North Korea,” said the official. “We have not been able to determine at this point whether it was in fact nuclear.”
Hat tip to Richard Fernandez, who wonders:
Could this one have been a suitcase bomb?