Almost 60,000 homes across Hampshire are without water because of a "technical issue" at a Southern Water supply works, the company has said.
Homes in Southampton, Romsey, Eastleigh, Totton, and parts of the New Forest have been affected by problems at the Testwood water supply works preventing water from leaving the site.
Southern Water apologised and said it was working hard to restore supplies, but warned the issue might continue until the weekend.
Long queues have been reported at bottle stations which have been set up at the Places Leisure Centre in Eastleigh, Sainsbury's superstore in Southampton and Asda superstore in Totton.
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Southern Water said it is continuing to deliver water supplies to customers registered on its priority list and estimates that around 58,000 homes have been affected.
It said the company has supplied dedicated tankers to Southampton General Hospital and Princess Anne Hospital.
Several schools in the area say they are unlikely to open today.
At 7am on Thursday, Southern Water said in an update: "Overnight our teams have fixed the problem at the Testwood Water Supply Works and restarted the site.
"We're now filling up the reservoir again with drinking water, ready to restore supply.
"This is a gradual process which must be done carefully and safely, but customers will start to be reconnected later today."
Bottled water has been delivered to care homes and vulnerable customers, Southern Water said.
It is setting up bottling stations across the region and will provide more details on these later on Thursday.
"We are so sorry for the disruption this has caused you," the company added.
In a statement on its website, Southampton General said: "We are working with Southern Water on contingency arrangements to ensure our hospitals continue to maintain water supplies."
The hospital added: "We ask patients to continue to attend appointments as planned but to allow extra time for their journey and in accessing parking facilities, due to the access requirements being put in place to enable delivery of those supplies."
Southern Water said earlier the issue may not be fully resolved until the weekend.
"We are working towards all customers being back in supply by the weekend," it said.
(c) Sky News 2024: Tens of thousands of homes could be without water until weekend, says Southern Water
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