(CNN) -- Lighthouse keeper J.A. Eckerman was the last person to see World War II Soviet submarine S-2 before it sank in January 1940 between Sweden and Finland.
A team of Swedish and Finnish divers had been searching for the Soviet submarine S-2 since 1999.
As the submarine dove near the island of Market, northwest of Aland, Eckerman heard a loud explosion and saw smoke rise from the water.
The long-lost wreck was missing for 69 years until a team of Swedish and Finnish divers -- including Eckerman's grandson Ingvald -- discovered it this year.
What remains of the sub was found between the Swedish coast and the Finnish island of Aland, northeast of Stockholm, in late February, the divers announced Tuesday.
The submarine was very badly damaged by the explosion, said Marten Zetterstrom, one of the divers. The front gun is still there, and a torpedo is still in one of the tubes, but about 20 meters (about 65 feet) of the vessel is missing.
The search had been going on for nearly 10 years, the divers said in a news release.
The sub had a crew of 46 and four passengers when it sank.
Sweden and Finland claim credit for sinking the submarine with mines. Russia has contacted Swedish and Finnish authorities to clarify what caused the submarine to sink, the divers said.
Finland was at war with the Soviet Union at the time the sub sank. A deal between Germany and the Soviets had put the Nordic nation within the Soviet "sphere of influence," and Soviet troops had invaded Finland late in 1939.
The fighting was mostly confined to Finland's eastern border. Just two months after the submarine's sinking, a temporary peace agreement was reached.
Sweden remained neutral in World War II.
CNN's Per Nyberg contributed to this report.