Research is underway to learn more about the origins of medieval sword found earlier this month at the bottom of a Polish river, which some experts believe may have belonged to the Vikings.

We know that these so-called Ulfberht swords were produced somewhere in Central Europe, but it’s not known exactly where,” Sambor Gawiński from the Polish conservator office told local news.

Workers made a surprising discovery in Poland when they pulled an early medieval sword from a muddy riverbed while dredging, and some researchers think the weapon could have a Viking connection.