HONG KONG — Hong Kong health authorities say a 54-year-old man infected with swine flu has died but it was unclear what caused his death as he was also suffering from chronic lung disease.

The Kwong Wah Hospital said in a statement late Monday that the man suffered from a chest infection with shortness of breath and cough when he sought emergency treatment Sunday. It says the man tested positive for swine flu just hours after he went into cardiac arrest.

He died Monday bringing the city's death toll related to the virus to four.

It says the man was also admitted to another hospital last week for chronic lung disease treatment but left Saturday against medical advice.

The first two swine flu-related deaths in Hong Kong were Filipinos - a seaman and a domestic helper.