Almost 5,000 coronavirus cases have emerged that are suspected to be linked to a music festival in Cornwall earlier this month.
Health officials are investigating 4,700 cases after the Boardmasters event two weeks ago.
The cases are spread across the country but around 800 are living in Cornwall, a council official confirmed.
He said people who tested positive for Covid-19 reported they had been to the festival, held between August 11 and 15 in the Newquay area.
The all-ages festival, which included headliners Foals and Gorillaz, outlined its Covid-19 policy on its website.
It said the festival would ask all ticket-holders aged 11 and over to demonstrate their Covid-19 status through the NHS Covid Pass app before entering.
This meant attendees had to provide proof of a negative lateral flow test taken within 24 hours of arrival at the festival gates, proof of being vaccinated with both doses (with the second received at least 14 days before the festival), or proof of natural immunity following a positive PCR test (provided it had been at least 10 days and up to 180 days after taking the test).
People who camped at the festival had to take a second NHS lateral flow test during the event on Friday August 13 and log their results in the NHS Covid Pass app.
Attendees had to bring their own lateral flow tests.
Face masks were not compulsory but were encouraged.