Hamas’ armed wing the Al-Qassam Brigades said on Thursday that seven members died after a tunnel on the Gaza-Israel border which they were working to rebuild collapsed.
It said the collapse occurred on Tuesday night due to heavy rains and it took two days to find the bodies before making an announcement.
Three other members managed to escape before the collapse and a fourth was rescued later, the group said.
Egypt, after a military coup overthrew the country's pro-Palestinian government in 2013 destroyed the majority of the tunnels connecting it to Gaza.
In September, in an attempt to close down the last remaining cross-border tunnels linking Egypt to neighbouring Gaza, the Egyptian military began flooding the tunnels to create fish farms.
Israel also heavily damaged and destroyed Gaza's tunnel network during a 50-day long offensive in 2014.
The tunnels are of vital importance to Hamas and its members in case of a potential assault by Israel. The people of Gaza also use the tunnels to bring supplies in and out of the blockaded enclave.
Such tunnel collapses have previously occurred in the coastal strip, which is under an Israeli blockade and has been the subject of three offensives since 2008.
On Saturday a tunnel collapse killed a 30 year old man, Hamas officials said.