The Palestinian Interior Ministry in Gaza announced on Thursday that three Palestinian workers were found dead inside the tunnel used to smuggle goods from Egypt to the besieged Gaza Strip.
According to the Interior Ministry, toxic gas was injected into the tunnel from the Egyptian side while the workers were working inside.
On Friday, Palestinian factions in Gaza condemned the "killings" of the workers, blaming the Egyptian authorities for their deaths.
In 2013, the Egyptian authorities started a wide-scale campaign on the border tunnels between Gaza and Egypt. The tunnels are used to smuggle basic living necessities to the coastal enclave that has been under strict Israeli siege.
Hundreds of tunnel workers have died inside the tunnels since the Israeli siege on the Gaza Strip in 2007.
Opinion: The Israeli-Egyptian siege of the Gaza Strip must end unconditionally without delay