TAIPEI -- Taiwan's disease control authority said Monday that four of seven suspected human infections of H7N9 bird flu that were reported over the last 24 hours have been ruled out, although the remaining three cases are still being tested.

Twenty-seven suspected cases have been reported on the island since April 3, with 24 of the patients testing negative for the virus, Chang Feng-yee, chief of the island's disease control authority, said at a press conference.

However, Chang did not provide details about the three people who are still undergoing tests.

The island has enhanced surveillance and intensified the sanitization of poultry farms as preventative efforts against the H7N9 bird flu, as the the mainland has reported an increasing number of cases.

Twenty-one cases have been reported on the mainland thus far, appearing in Shanghai and the eastern provinces of Zhejiang, Jiangsu and Anhui. Six of the cases have resulted in death.