The U.S. 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 sub, 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 Tuesday night, said spokesman Phil McGuinn.
The Navy immediately started searching and also contacted the International Submarine Escape and Rescue Liaison Office. Family members of the estimated 140 sailors on board also were notified, reports AP.
"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.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969