A few attendees at Sunday's sale took one look at them and became concerned enough to call police in Kettering, a suburb of Dayton, WHIO-TV, Dayton, reported.
"Instead of having a pin like American [grenades] have, they had string," said Larry Hyatt, conductor of Sunday's estate sale. "And it was really rotten-looking string."
Because old explosive devices can be sensitive to radio frequencies, Kettering police stopped using their radios and advised those close to the sale's locale not to use their cellphones.
"If you have old ammunition and things, that [the explosives] can be a hazard -- especially if you don't have them secured properly," Kettering police officer Ron Roberts said. "You need to contact your local law enforcement agency and have them disposed of properly. If you're unsure, we can come out and check them."
After the bomb squad confiscated the grenades they detonated them in an open field, WHIO-TV said.