Egypt on Thursday denied pumping poisonous gas into a smuggling tunnel under Gaza's border which led to the death of four Palestinians, following accusations from the Islamist Hamas movement.
It is "entirely false of course," foreign ministry spokesman Hossam Zaki told AFP, without elaborating.
Egypt has been under pressure to shut down the hundreds of tunnels that are a key economic lifeline for the blockaded Palestinian territory but which are also used to bring in weapons for the Islamist armed group.
An Egyptian intelligence official confirmed that Egyptian security forces destroyed the entrances to several tunnels this week, but said that no gas was used in the operations. He said that Egypt routinely blows up the mouths to the tunnels to seal them off, and that the blast and an ensuing fire could quickly use up all the oxygen in the confined space, causing people caught inside to suffocate.
It was not immediately clear what evidence Hamas was basing its allegations on.
Mohammed al-Osh, the medical director of the Abu Yusef al-Najar hospital in the Gaza border town of Rafah where some of the dead and injured were taken, could not confirm those killed had inhaled poison gas. He said the hospital did not have the equipment or specialists needed to conduct the necessary tests on lungs and clothing.
Pumping gas into tunnels
Earlier Hamas accused Egyptian security forces of pumping gas into the tunnel. Palestinian medics working for the Hamas-run health ministry said the four had died from suffocation and that there was evidence of toxic gas.
"Hamas holds the Egyptian side responsible for the killing of four innocent workers after Egyptian security forces pumped poisonous gas into one of the tunnels," Hamas spokesman Sami Abu Zuhri told reporters in Gaza.
Israel and Egypt have kept Gaza's official border crossings closed since Hamas seized control of the coastal strip in 2007 from forces loyal to Western-backed Palestinian President Mahmoud Abbas, who now only governs in the West Bank.
The United States and Israel have been pushing Egypt to do more to try to close the tunnels, which provide Hamas with a lifeline helping it to stay in power in Gaza. Weapons and other contraband regularly move through the tunnels.
But the 1.5 million residents of the impoverished Gaza Strip also rely on the tunnels to bring in food and commercial goods like refrigerators and clothing.
Many of the tunnels, dug with electrical drills and running side by side under the border, are just high enough to enable workers to move on all fours. Their entrances are covered by tents and they are equipped with motorized pulleys to haul goods and generator-powered lighting.
Palestinian officials in Rafah say Egypt has stepped up a crackdown on smuggling in recent months, blowing up numerous tunnel entrances on its side of the border, setting up checkpoints in the area and confiscating contraband. Since December, Egypt has also been building an underground steel wall to block the tunnels.
Rafah officials have said about four miles (six kilometers) of that barrier -- covering roughly half of the border area -- is already complete.
The officials say the Egyptian measures have led to a sharp slowdown in tunnel traffic in recent months, pinching the local economy.