"The three Palestinian workers who disappeared this morning on the Palestinian-Egyptian border have been found and returned safely," Hamas interior ministry spokesman Iyad al- Bozom said in a statement, providing no further details.
A security source told AFP "the three were kidnapped by mistake by gunmen probably belonging to an extremist Salafist group but were returned because they were not the target."
The three men are currently under investigation at the interior ministry in Gaza, the source said.
The account of the witness, who spoke on condition of anonymity, was not confirmed by authorities.
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Egyptian security forces have been fighting a branch of the Islamic State group in the Sinai, and the extremists have recently stepped up their attacks.
In August, a suicide bomber killed a Hamas guard along Gaza's border with Egypt in what was described as a rare Islamist attack against the Palestinian group.
In 2015, gunmen seized four Hamas members from a bus bound for Cairo from the Gaza Strip in the Sinai near the border.
Tunnels between Gaza and Egypt are typically used for smuggling.
The Gaza Strip has been under an Israeli blockade for more than a decade, while Egypt has also kept its border with the Palestinian enclave largely closed in recent years.
Hamas and Israel have fought three wars since 2008.