Police were back at the spot in the Charles River in Needham, Massachusetts, where two old explosives were previously found for a new, precautionary sweep Monday.
A large police presence was seen by the Kendrick Street bridge, and Needham police asked the public to avoid the area, though they noted there was no risk to the public.
"If an ordnance is located, we will work in conjunction with the Massachusetts State Police Bomb Squad to determine appropriate disposal of the item in the safest manner possible," the agency said in a Facebook post alerting the community of the sweep of the river.
After hours of searching, no ordnance was found on Monday, though a cylindrical tank was pulled from the water. It was being checked over but didn't appear to be dangerous, according to a state police spokesman.
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It wasn't immediately clear what prompted the new search.
The previous unexploded devices were found by magnet fishers, who throw powerful magnets in waterways and reel them in, hoping to drag out metal objects.
Josh Parker pulled up a hollow bazooka round at the Kendrick Street bridge on Wednesday, days after his friend, Sean Martell, pulled up a live mortar in the same area.
On both occasions, Needham police shared alerts with residents about possibly hearing the ordnance be exploded in a controlled detonation in town.
"It was fairly common for soldiers to bring back souvenirs from their time in the war, when they came home," said Needham History Center & Museum Executive Director Gloria Greis.
She said she wouldn't be surprised if someone simply discarded these pieces of ordnance in the river to try to get rid of them, but doesn't believe they come from any nearby military facilities.
"The only military installation in Needham was a Cold War post-1950 missile site that was known as the Nike site," Greis said. "And those were originally surface-to-air and then later ICBM missiles. So they have nothing to do with the ordnance that were found."
