Five Sri Lankan fishermen who had consumed the contents in a bottle floating in the sea on Saturday had died by Sunday afternoon, Navy Spokesman Captain Gayan Wickramasuriya said.
The navy spokesman said the victims are a part of a six-man crew that sailed from the Tangalle Fisheries Harbour, reported Xinhua news agency.
They found the bottle around 320 nautical miles off the coast and had consumed its contents believed to be alcohol, he said.
Wickramasuriya said one survivor is in critical condition and currently receiving emergency treatment.