GAZA STRIP - Hamas officials blamed Egypt for the deaths of four Gazans working in one of the smuggling tunnels dug underneath the border between the Egyptian Sinai and the Gaza Strip.
Egyptian security forces pumped gas into the tunnel, killing four workers and injuring six others.
"The Hamas Interior Ministry confirms that the citizens' cause of death was the Egyptian security forces spraying poison gasses into one of the tunnels," read a statement issued after the incident.
A Hamas official in charge of the area told The Associated Press on condition of anonymity that Egyptian border guards pumped gas used to disperse crowds into the tunnel.
Hamas spokesman Fawzi Barhoum said Egypt owed them an explanation.
"This is a terrible crime committed by Egyptian security against simple Palestinian workers who are trying to earn their daily bread," Barhoum told AP.
"The United States and Israel have been pushing Egypt to do more to try to close the [smuggling] tunnels to bring in food and commercial goods like refrigerators and clothing," he said.
"We demand thata Egypt explain its position about what is happening and investigate the circumstances of this terrible crime and show the truth to the entire world and hold those responsible accountable," Barhoum said.
In recent months Egypt has stepped up efforts to thwart smuggling by Hamas, blowing up tunnel entrances on the Egyptian side, beefing up security forces and checkpoints along the border and seizing contraband.
The tunnels, used by Hamas to smuggle weapons and ammunitions into the Gaza Strip, have become a source for a wide variety of other products and goods.
AP contributed to this report.