The United States Navy intercepted a ship suspected of carrying illegal weapons shipments of out North Korea late last month, but was unable to confirm those suspicions when the ship fled and refused to let the Navy on board, Pentagon Spokesman Col. Dave Lapan told reporters Monday.

One U.S. official, who spoke to Fox News on the condition of anonymity, said it is believed the ship was carrying "missile technology."

On May 26th in the South China Sea, the guided missile destroyer USS McCampbell hailed the Belize flagged ship after receiving intelligence about the possibility it was carrying illicit cargo.

Shortly after approaching the cargo ship the McCampbell received permission from officials in Belize to board, but the ship's master, believed to be North Korean, refused.

The McCampbell tracked the suspicious ship for three days in the South China Sea when on May 29th the ship turned around and headed back for North Korea.

Pentagon and State Department officials declined to provide specific information about what it believed was on board, but they say the ship's behavior was telling. "The ship's master refusing us permission to board as well as the fact that it turned around speaks to some of our concerns about its cargo," State Department spokesman Mark Toner said Monday.

Although the McCampbell did not follow the ship all the way to port, Pentagon officials confirmed it made it back to North Korea. "We have other ways of monitoring these things," Lapan said.

The USS McCampbell is currently at homeport in Yokosuka, Japan.

United Nations Security Council resolutions 1718 and 1874 prohibit North Korea from proliferation of most weapons, including nuclear weapons parts and missiles.

In June of 2009 the USS John McCain and the USS McCampbell were both involved in a tense standoff with the North Korean flagged Kang Nam cargo ship, also suspected of carrying illicit weapons. At the time the North Koreans threatened that any interception of the ship would be considered "an act of war." After being tracked intensely by U.S. and other international naval ships, the Kang Nam eventually returned to port in North Korea in July. It's believed the ship had the intent to offload a small arms shipment in Burma.

North Korea has a history of illegally providing material related to the production of nuclear weapons to its allies. Toner said the State Department has recently called on Burma to "obey their non-proliferation obligations."