The UK Safety and Health Agency reported the crypto water bug outbreak more than 24 hours before South West Water issued its notice to residents telling them to boil their tap water.

The news comes as the number of confirmed cryptosporidium cases in Devon has shot up to 100.

The water parasite was detected in the tap supply in Brixham and surrounding areas last month, causing people to fall ill with symptoms that include watery diarrhoea and vomiting. Two people have so far been admitted to hospital.

The UKHSA reported the crypto outbreak on Monday May 13.

And there were reports of people falling ill almost two weeks before SWW announced its boil notice early on Wednesday May 15.

It can take between 2 and 12 days for people to become unwell after being exposed.

Sarah Bird, health consultant for UKHSA, said: “The data shows the outbreak is associated with people who live in, or visited, the boil water notice area of Brixham and the nearby areas before the (boil) notice was put in place.”

A boil water notice remains in place for about 2,500 residents in the Hillhead, upper Brixham and Kingswear areas. (Monday June 3).

Ms Bird said further cases may appear due to the time lag between exposure and falling ill, but added that the number of cases being reported was slowing down.

Meanwhile, SWW has spent the last week cleaning its reservoirs and flushing the network “several times” in an attempt to remove the remaining traces of cryptosporidium.

Despite this, water tests have shown that “further intense work” is needed to completely wipe out the parasite.

On Friday (May 31) SWW said it would start “the next stage”, cleaning pipes between the Boohay supply tank and Kingswear by pumping a high-pressure ice solution through the pipes.

Affected residents will receive an additional £50 credit to customer bills for the inconvenience caused.

SWW CEO Susan Davy had been due to appear before a parliamentary committee on June 5 to explain her handling of the crisis, but the meeting has been postponed due to the upcoming general election.