Wastewater pumping stations in one of Gaza's main cities stopped working on Tuesday because fuel had run out, the local authority said, expressing fears that disease could rapidly spread.
Tens of thousands of people displaced by the Israel-Hamas war have sought shelter in Deir al-Balah, and city authorities said more than 700,000 people could be at risk from a "health and environmental crisis".
"Deir al-Balah municipality announces the halt of water waste pumping stations because stocks of fuel necessary for their functioning are exhausted," said a city statement.
It predicted that "roads will be flooded by waste water" and "diseases will spread".
Gaza has had no electricity supplies since the war was unleashed by the October 7 Hamas attacks on Israel. The fuel-powered waste plants treat water that is then put into the Mediterranean.
"Nineteen pits and two large reservoirs are unusable in Deir al-Balah," Ismail Sarsour, an official with the city's emergency committee, said ahead of the release of the statement.
He said the stations handle wastewater for more than 140 points of shelter where tens of thousands of people have taken refuge.
The Palestinian Authority's water department, the PWA, which is based in Ramallah in the occupied West Bank, said recently it had arranged for tens of thousands of litres of fuel to enter Gaza.
But Palestinian experts said the water crisis is so deep that the fuel alone would not help. Sarsour and the experts said there was also a critical shortage of spare parts to repair damaged infrastructure.
Israel said this month that, with help from the UN children's agency UNICEF, it has connected one desalination plant in southern Gaza to its electricity network. It is unclear if the plant has started working.
The Palestinian Authority also said Tuesday that it expected electricity supplies to start again in central Gaza in "coming days" to power public infrastructure. Israeli authorities have not confirmed the move.
Israel's military offensive since October 7 has killed at least 38,713 people, mostly civilians, according to figures from Hamas-run Gaza's health ministry.
The war began with Hamas's unprecedented attack on Israel which resulted in the deaths of 1,195 people, mostly civilians, according to an AFP tally based on Israeli figures.