WASHINGTON -- US intelligence agencies have concluded that last week's nuclear test by the Democratic People's Republic of Korea (DPRK) was fuelled by plutonium, the New York Times reported Tuesday.

The newspaper quoted unidentified officials as reporting that the explosion was most likely not fuelled by uranium, but rather by plutonium harvested from its small nuclear reactor.

The DPRK announced on Oct. 9 that it had successfully conducted its first nuclear test.

U.S. authorities and intelligence officials were reportedly watching for indications that the DPRK might be preparing for a second nuclear test.

"The DPRK have made no secret of their desire to be provocative. The first test did have a low yield and perhaps it would not be unreasonable to expect that they would like to try to something again," White House spokesman Tony Snow said on Tuesday.