A U.S. Marine Corps helicopter that was assisting in Nepal disaster-relief operations is missing, according to U.S. officials. Navy Capt. Chris Sims says the aircraft from Marine Light Attack Helicopter Squadron 469 disappeared Tuesday near Charikot, Nepal. The number of people on board was not disclosed. An investigation into the disappearance is underway. A 7.3-magnitude earthquake shook Nepal Tuesday, just weeks after a 7.9-magnitude quake left 8,000 dead.