Updated at 6.14pm: Hong Kong health officials investigating the deaths of two pig farmers from acute pneumonia said on Friday that Guangdong had confirmed that a pig farmer there had died from a similar disease this month. Centre for Health Protection consultant Thomas Tsang Ho-fai on Friday said the mainland case involved a 48-year-old pig farmer in the Guangdong city of Foshan. The farmer fell ill early this month and died two weeks later of acute pneumonia caused by an infection, Dr Tsang said. Tests for bird flu, Sars and the pig-borne bacterium Streptococcus suis all showed negative results but doctors had no idea which virus or bacterium had caused the farmer's illness, Dr Tsang said. The news came as Hong Kong health authorities were trying to track down the cause of death of two local farmers. The pair, aged 44 and 65, died of acute pneumonia in hospital in June and this month, days after developing symptoms. The centre has said previous tests could not identify a virus or bacterium which would cause their illness. Dr Tsang said no apparent links were detected between the cases of the Hong Kong farmers and that of the Foshan one, in terms of time and place of infection. But he said authorities would continue their investigations and step up monitoring of local farms, through such procedures as extracting samples from pigs for tests. Dr Tsang added that the centre would liaise with public hospitals and private doctors to keep a lookout for any cases of pig farmers diagnosed with pneumonia.