An unusual cluster of HIV cases has been discovered in the small Cornish resort of St Ives, health chiefs revealed yesterday.

The local primary health care trust took the rare step of calling a press conference to announce the disturbing finding and warn other residents in the close-knit community that they may be infected.

Health officials set up a hotline to field calls from worried residents of the harbour town, renowned throughout the world for its artists' colony and as the home of the Tate's Cornish outpost. Today and next week clinics will be run in St Ives and in Truro so that people can be tested.

The trust said people may have been infected eight years ago or longer and residents of ages ranging between 20 and 60 could be at risk.

It refused to give any details of the men and women - up to 10 of them - who have been found to be infected. However it is understood that a local heterosexual man is at the centre of the scare. The health authority felt it had to go public because it has not been able to trace all his sexual partners or identify others linked to them. There is no suggestion that the man was deliberately infecting others and the police have not been involved.

At the press conference yesterday the West of Cornwall primary health care trust said the situation had come to light only in the last month.

David Miles, director of public health, said: "We hope that there aren't more people who have contracted HIV - however we think it is quite possible that there may be. Our investigations so far suggest that people will have been at risk for at least the last eight years, and possibly longer.

"It also seems that those at risk are in a wide range of age groups, from young adults through to men and women in their 50s, who have had unprotected sex. People may have contracted HIV and not yet be experiencing symptoms."

There was scepticism from some health professionals about the decision to go public as it is thought such a move could drive people underground, as well as causing panic. Dr Miles said the trust had consulted with the health protection agency before making its announcement. It felt it had to act as it did because it was not certain it could trace all the partners of those involved.

The trust's revelation dominated conversation in St Ives' cafes, pubs, beaches and art galleries yesterday. Emerging from the surf on Porthmeor beach, Steve Jones, 32, said: "It's a real shock. Everyone's been looking around, wondering has he got it, has she got it? Have I got it?"

Bar worker Sam Duda, 24, said: "It does worry you. I think lots of people will be confused and just go and get tested because they are not sure. There will be a lot of people panicking. I think the lines and clinics may be overworked."

Plumber, Ian Bird, 49, said: "It's concerning to think that somebody might be out there infecting people. I will have a word with my kids and my friends to make sure they all know to be careful. You don't really expect it in a place like St Ives."

In relative terms the cluster is large. Between 70 and 80 people in the whole of Cornwall are being treated for HIV or Aids. In 2004 - the most recent years for which figures are available - there were only 49 new cases in the whole of Cornwall and Devon.

The move to go public is rare but not unprecedented. Eight years ago health chiefs in Doncaster, South Yorkshire, identified 10 cases of HIV, five of which were linked to one heterosexual man.

But fears are bound to be even more acute in St Ives because of its size - only around 6,000 people live in the picturesque centre of the fishing town.

Artist Alexandra Dickens said: "It's a very small community. You come across the same people again and again. People break up and move on, relationships overlap. I should think a lot of people are very frightened at the moment."

HIV may be passed on through unprotected vaginal, anal or oral sex. Unprotected sex is sex without a barrier such as a condom. There is also a risk with condoms that split during sex.

Any individual who is concerned they may be at risk can be tested for HIV through the genito-urinary medicine service. A dedicated, confidential helpline number is available on 0845 850 9850.