South Korean intelligence officials say North Korea is digging a new underground tunnel in what appears to be preparation for a third nuclear test, according to The Associated Press.

A report written by intelligence officials and shared Monday with AP says recent satellite photos show piles of dirt near the newly excavated tunnel's entrance.

The report says the excavation at the North's northeast Punggye-ri site is in its final stages. Experts say dirt is needed to fill up underground tunnels before a nuclear test.

The report's release comes as North Korea prepares to fire a long-range rocket April 12-16 that Washington and others say is a cover for testing missile technology that could be used to fire on the United States.