A strong message Queenstown businesses must carry on boiling water to keep themselves safe

Health authorities have concluded the most probable source of the cryptosporidium outbreak is human faecal contamination of the water supply.

Te Whatu Ora says it's likely been collected into the Two-Mile water treatment plant before going out to businesses and homes.

A boil water notice will remain in place.

Medical officer of Health, Dr Michael Butchard says they understand how difficult it's for residents and businesses.

He says they're grateful they're continuing to boil water to keep each other safe and don't underestimate the inconvenience its caused.