Leftover ordnance exploded Thursday as residents in the southern Gaza Strip cleared rubble from a house destroyed in last summer's war with Israel, killing at least four people and injuring about 20 others, medical officials said.
Witnesses described a huge blast. The dead and injured were brought to the hospital in Rafah, said Gaza Health Ministry spokesman Ashraf Qidrrah.
The United Nations Mine Action Service has worked with local security teams to clear unexploded munitions left from a series of confrontations with Israel since 2009.
According to the agency, nearly 7,000 explosive remnants remain buried in the rubble from the 2014 war, "a significantly higher level of contamination than previous conflicts."
Six people were killed in August 2014 when an unexploded bomb detonated during attempts to remove it. The victims included Italian journalist Simone Camilli and local reporter Ali Shehada abu Afash.
As of May, 11 Palestinians had been killed and 123 injured in such explosions since the cease-fire last August, according to the U.N. Office for the Coordination of Humanitarian Affairs.
Rafah was heavily bombed during the 50-day conflict between Israel and the Palestinian militant group Hamas last summer, following the capture of an Israeli soldier in the area.
A report issued last week by the London-based rights group Amnesty International said evidence suggested that Israel deliberately targeted residential areas of Rafah, actions that could amount to war crimes. Israel's Ministry of Foreign Affairs refuted Amnesty's charges.