GAZA CITY, Gaza Strip (AP) — Gaza’s ruling Hamas militant group on Friday said it recovered the bodies of three men from a smuggling tunnel along the Egyptian border.

The statement gave no cause of death. But a day earlier, the group accused Egypt of pumping poisonous gas into the tunnel. Such accusations could escalate tensions with Egypt just as the Egyptians are trying to broker a cease-fire agreement between Hamas and Israel. There was no immediate Egyptian comment.

Contact was lost with the smugglers late Thursday. Hamas and other militant factions later said that workers had died when toxic gas was pumped into a “trading tunnel,” calling it “murder for which Egyptian authorities bear full responsibility.”

Israel and Egypt imposed a crippling blockade on Gaza after Hamas seized power from rival Palestinian forces in 2007. Israel says the blockade is necessary to prevent the Islamic militant group from smuggling weapons into the territory. Rights groups say the blockade amounts to collective punishment of Gaza’s more than 2 million Palestinian residents.

For years, Palestinians used a vast network of tunnels beneath the Gaza-Egypt border to smuggle in everything from food and fuel to home appliances and motorcycles. Israel and Egypt said the tunnels were also used for weapons smuggling.

In 2013, Egypt began cracking down on the tunnel trade, demolishing tunnels as well as homes in the town of Rafah, which straddles the frontier, in order to create a buffer zone on its side of the border. Authorities said residents would be compensated.

Egypt has been leading mediation efforts since Israel and Hamas fought an 11-day war in May, their fourth since Hamas seized power. Hamas has demanded the easing of the blockade in return for calm, and in recent weeks has organized violent demonstrations along the frontier with Israel.

Egypt often serves as a mediator between Israel and Hamas, and its efforts to secure a broader long-term truce have shown signs of progress in recent days. Israel this week eased the blockade to allow construction materials needed for postwar repairs into the territory. And Israel’s prime minister, Naftali Bennett, is scheduled to visit Egypt this month.

It was not immediately known what effect Hamas’ accusations would have on the cease-fire efforts.