A drinking water supply to a residential army camp has been contaminated with diesel.
Residents at RAF Upavon in Wiltshire have had bottled water delivered and have been unable to flush the toilets or use their showers.
Supplier Ancala Water issued a "do not drink" notice in response to potential risks to health.
The Ministry of Defence (MoD) said it is working to determine the cause of the contamination.
According to a letter sent to residents, the diesel leaked into land and the bore hole which supplies water to Upavon Station and the Service Families Accommodation.
Once the contamination was detected, the bore hole was isolated.
The letter also said: "Although results are improving the timeline for the return to normal use cannot presently be confirmed."
An MoD spokesperson said: "Those in affected areas are being asked not to drink water from the taps.
"External water tanks and bottled water are available for those affected. Alternative shower and laundry facilities have been made available.
"We are working with our contractors to determine the cause of the issue, and to come to a solution as soon as possible."
Danny Kruger, the MP for Devizes, said: "I have contacted the Army Families Federation for more information and to offer my help with liaising with the relevant agencies."