More poultry workers are being tested after five people were infected with H5N1 bird flu at a farm in northeast Colorado, officials said Tuesday, as an investigation continued to determine what caused the unusual cluster of human cases. AnneMarie Harper, a spokeswoman at Colorado Department of Public Health, said 69 symptomatic workers had been tested so far, including 7 last Thursday, 46 last Friday and 16 more on Monday. At least 5 of those workers were found to be infected with bird flu but other tests were still being processed on Tuesday. The exact number of pending test results was not i…