A small earthquake has been detected in an area of North Korea were previous nuclear tests have been carried out, the U.S.Geological Survey reported Thursday.

The USGS said the magnitude 2.9 quake occurred about 13 miles northeast of Sungjibaegam, North Korea, "in the area of the previous North Korean Nuclear tests.."

"The event has earthquake like characteristics, however, we cannot conclusively confirm at this time the nature (natural or human-made) of the event," the USGS notes. "The depth is poorly constrained and has been held to 5 km (3 miles) by the seismologist."

The USGS added that the Air Force Technical Applications Center is the only organization in the federal government whose mission is to detect and report technical data from foreign nuclear explosions.

The detection of a quake does not always indicate a nuclear test. On Sept. 23, a magnitude 3.4 quake was registered under Mt. Mantap, an area of North Korea where earthquakes do not normally occur.

A joint report published by the Chinese Academy of Sciences and UC Santa Cruz concluded that tunnels in the test site collapsed, the Los Angeles Times reported.

North Korea has carried out six nuclear tests since October, 2006.