The thefts are believed to have taken place during the summer months of this year.
According to the National Board of Antiquities, two 19th century shipwrecks, the steamship Sandviken and a trading vessel, the Edmund, have both been targeted by thieves. The Sandviken, in waters off Kirkkonummi in the south, has had its ship's bell stolen. The aft cabin of the Edmund, in waters near Järvön in the Gulf of Bothnia, has been emptied of objects including bottles and clay jars. The structure of the Edmund has also been damaged.
Thieves have also taken porcelain dishes and bottles from the wreck of an 18th century warship in waters off of Porvoo.
Experts say that without proper conservation, objects brought up from the wrecks will not survive for long.
Old shipwrecks are protected by law. Divers are allowed to visit such sites, but the wrecks and associated artifacts may not be disturbed or in any way damaged.