LONDON, May 26 (Reuters) - Vets investigating an outbreak of a strain of bird flu in Wales have ordered tests on birds at a second farm, officials said on Saturday.

Authorities confirmed an outbreak of bird flu on Thursday among chickens at a farm in Denbighshire, North Wales.

But it was the low pathogenic H7N2 strain of bird flu, not the H5N1 strain, which is potentially deadly to humans and has caused scares elsewhere in the past.

Officials say two people who visited the farm or had been in contact with the infected birds had tested positive for H7N2. They said it was very rare for humans to become infected with bird flu and the risk to the general public was low.

Christianne Glossop, Wales´s chief veterinarian, said on Saturday she had ordered samples to be taken from birds at a second farm, this time on the Llyn Peninsula in Wales.

She said she had ordered the tests because of a link between the farm and a market in Chelford, western England, where the chickens at the first farm had been bought.

"There is a police presence currently at the farm, to ensure no unnecessary access to the premises," Glossop said in a statement.

"A decision on any further action required regarding birds on the farm will be taken on the basis of the test results."

Britain has been on the watch for bird disease after Europe´s biggest turkey producer Bernard Matthews was forced to destroy 160,000 turkeys because of an outbreak of the H5N1 strain of bird flu in England earlier this year.

The World Health Organisation says 186 people have died of bird flu since the H5N1 virus resurfaced in Southeast Asia in 2003. The virus has since spread throughout much of Asia, parts of Europe, the Middle East and Africa.

The presence of an H7 virus in poultry is treated seriously by animal health officials because scientists believe that, when allowed to circulate in poultry populations, a low pathogenic virus can mutate into the highly pathogenic form.