Fighting in east Ukraine has interfered with water treatment, producing a foul stench from the taps that aid workers say could bring health risks.

“The water has gone bad,” said Raisa Prilipko, head of a Donetsk orphanage that gives shelter to 21 preschool children. “We remove sediment and boil water, we filter it to minimize any risks to the children’s’ health.”

The water supply system in the Donetsk region of east Ukraine has suffered repeated damage during almost a year of fighting between Ukrainian government forces and Russia-backed separatist rebels that has killed more than 6,000 people.

The regional water company, Donbas Water, says it is still safe to drink. The smell is a result of a shortage of purification chemicals like chlorine, which have not arrived from territory under Ukrainian government control and are being used in smaller amounts than normal.

The International Rescue Committee, an aid organization looking into the water situation, said it believes the water may no longer be chlorinated at all.

“I wouldn’t drink it and I would not advise anyone to drink it without further treatment,” Bibi Lamond, the IRC’s eenior environmental health coordinator, said earlier this week. Bacteria numbers were bound to increase as temperatures were warming, she added.

“In the last two weeks we’ve seen quite a substantial deterioration in the turbidity of water and there is this very strong fishy, earthy smell. … People are being quite heavily impacted by this dramatic change in the quality of water.”

The main filtering station for Donetsk, a rebel-held city with a prewar population of 1 million, has been out of order since mid-January, Donbas Water says.

However, there has been anecdotal evidence of an improvement, with the smell less overpowering in recent days.

A sources who declined to be identified said chlorine supplies had started arriving under strict security from Russia. This would be sensitive, because Russian support for the rebel areas is a point of contention in the war.

The utility’s headquarters are located in Donetsk and 70 percent of its water usage is in rebel-held areas, but it also serves government-held territory. Its water supply is fed from open channels and pipes located mainly in territory held by the Kiev government.

According to the company, eight of its workers have been killed and 10 wounded in fighting as they ventured out to fix damage to water infrastructure.