ISLAMABAD, Feb 26 (Reuters) - Pakistani authorities have found a fresh outbreak of the H5N1 bird flu in chickens, the fourth case in a month in the South Asian country, a government official said on Tuesday.

The new outbreak was confirmed on Monday at a poultry farm in Karachi, the country's biggest city and where authorities reported two cases early this month, the official said.

The last bird flu case was reported in a northwestern town on Feb. 16.

"Laboratory tests have confirmed the H5N1 virus on a farm that is located away from populated areas," said health ministry spokesman Orya Maqbool Jan Abbasi.

Before sending samples to Islamabad, the farm owner had culled chickens and dumped them in a well which, Abbasi said, was in violation of the rules.

"This was wrong," Abbasi said. "Now, we have sprayed the well and closed it."

There were about 10,000 birds on the farm, he added.

Several outbreaks of the H5N1 strain of avian influenza in poultry and other birds have occurred in Pakistan, most in the country's northwest, since it was first detected in early 2006.

Pakistan confirmed its first human death from the virus near the northwestern town of Abbottabad in December.

Poultry officials say sporadic outbreaks have badly hit the industry, which is estimated to be worth 200 billion rupees (around $3.2 billion) and employs about 1.5 million people.

There is no general alarm, however, and most Pakistanis continue to eat chicken.

(Reporting by Augustine Anthony; Editing by David Fox)

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