The Navy temporarily lost communication with a submarine off Florida's coast and sent ships and aircraft to search for the USS San Juan before the vessel was contacted early Wednesday, military officials said.
There were no problems with the nuclear-powered Los Angeles class sub, based in Groton, Conn., and the Navy was investigating the incident, the Naval Submarine Force said in a statement.
Units of the USS Enterprise Carrier Strike Group saw a red flare in the area where the sub was operating off the coast of Jacksonville, Fla., Tuesday night, said spokesman Phil McGuinn.
Defense Secretary Robert Gates was awakened in the early morning hours and told of the events, said Pentagon spokesman Bryan Whitman.
"The secretary of defense was notified at the time when the Navy felt that they had a sub in distress," he said.
The Navy immediately started searching and also contacted the International Submarine Escape and Rescue Liaison Office in Norfolk to assist with the efforts. Family members of those on board also were notified.
"Fortunately, the submarine established communications in the early morning hours ... and indicated that there were no problems; hence, units were able to stand down from the search and rescue that was already well under way," the Navy said in a release.
There were about 140 sailors on board, said Lt. Mark Jones, a Navy spokesman in Groton.