The ammunition, thought to be a shell from some kind of large gun, was found by a member of the public diving in the area. The find was made in the Kalixälven river, on the Tärendö island near Pajala in the far north of the country.
“My information is that the military used to conduct exercises near to where the shell was found,” Lieutenant Commander Anders Nordin of the Swedish Navy, leading the recovery operation, told The Local.
“The person who found it had experience of the military, so the report is credible.”
The water where the diver found the shell is 1.5 metres deep, Nordin said.
Military bomb disposal teams from the naval base on Muskö, near Stockholm, made their way up on Thursday, and were on site by late afternoon.
They are set to look at the shell, and determine whether it is live. If it is found to be live, they will conduct a controlled explosion.
“Local police are working with the military to seal off the area while the operation takes place,” Nordin said.
Asked whether it posed a danger, Nordin said:
“Clearly if it is live ammunition it is not good that it was found there.”
But, he added, old ammunition was found frequently in lakes and rivers and around coastal areas, especially near Stockholm and Gothenburg, and was disposed of without problems.