KUWAIT CITY (AFP) - Four Bangladeshi workers who had initially tested positive for bird flu in Kuwait have been cleared of the disease after further tests, the Kuwaiti health minister said on Thursday.

"We are happy to declare that the results of the tests ... in the referenced laboratory in Egypt have been negative," minister of health Maasouma al-Mubarak told reporters after the latest tests by the World Health Organisation.

On Wednesday, the four workers who had been culling infected chickens in Kuwait were tested positive in preliminary tests, but the ministry of health sent specimens to the WHO reference laboratory in Egypt for confirmation.

They would have been the first cases of bird flu affecting humans in Arab nations of the Gulf, had the cases been confirmed.

The four workers were admitted to Kuwait's infectious diseases hospital with flu-like symptoms on Tuesday. The men have been isolated in a special ward and were still at the hospital on Wednesday.

Since the outbreak of bird flu in Kuwait, 22 people have been admitted to hospital on suspicion of being infected, but later discharged after confirming they were healthy.

The Bangladeshis were part of government teams culling and burying hundreds of thousands of chickens in Wafra, south of Kuwait City on the Saudi border.

Kuwait has culled about 1.7 million birds, most of them egg-laying chickens in four commercial poultry farms, since confirming in February an outbreak of the H5N1 strain of the bird flu virus that is dangerous to humans.

A total of 106 cases of the strain have so far been confirmed in birds.

In November 2005, the Gulf state announced the first case of a bird infected with the H5N1 strain -- a flamingo at a seaside villa.

The H5N1 strain, the most aggressive form, has killed 170 people worldwide, according to WHO, and seen millions of birds destroyed.

H5N1 is an avian influenza subtype with pandemic potential, since it might ultimately adapt into a strain that is contagious among humans.