WASHINGTON, March 12 (UPI) -- A North Korean submarine stationed off the nation's eastern coast was reported missing by United States military officials who observed the vessel.
U.S. officials told CNN North Korea lost contact with the submarine, as spy satellites, aircraft and ships watched North Korean navy searched the surrounding ocean.
It is believed the submarine experienced some type of failure, although it is unclear whether it sunk or is simply floating beneath the sea.
"The speculation is that it sank," a U.S. official said, according to Sky News. "The North Koreans have not made an attempt to indicate there is something wrong or that they require help or some type of assistance."
News of the missing submarine came after Pyongyang made statements regarding joint military drills between the U.S. and South Korea.
The drills, which involve 17,000 members of the U.S. military and 300,000 South Korean troops as well as 55 U.S. marine aircraft and 30 U.S. and South Korean ships, led North Korea to warn of "pre-emptive" strikes.