A second Gazan was found dead Sunday after the collapse of a tunnel on the Egypt border, the interior ministry in the Islamist Hamas-run enclave said.
On Thursday, rescue services said seven men had been trapped in the collapse.
Five were rescued, but on Sunday the ministry said they had retrieved the body of Mohammed Abbas of Rafah, after announcing the death of a man named as Fadi Abu Dan.
A local civil defense official described the underground passage from the southern Gaza town of Rafah into neighboring Egypt as a "trade tunnel", a euphemism for smuggling tunnels via which goods, cash, weapons and fighters are transported into Gaza.
The cave-in was caused by Egyptian flooding of the border zone in its campaign to stop smuggling, the official told AFP.
Since January 26, at least 12 Gazans have been killed in five separate tunnel collapses with both Israel and Egypt operating against the diggers.
An Israeli blockade severely restricts the movement of people and goods into and out of the territory, as part of measures to prevent sophisticated weapons making their way into the hands of terrorists sworn to Israel's destruction. Egypt's sole border with Gaza has also remained largely closed since 2013.
AFP contributed to this report.