The secretary for innovation and technology dismissed rumors of "fake downloads" of the government-developed LeaveHomeSafe app, saying more than 97 percent of its downloads were made in Hong Kong.
About 2.79 million people downloaded the mobile application, which warns users of Covid-19 infections at locations they have visited, as of yesterday, including 2.61 million in Hong Kong and 42,303 in the mainland.
But critics alleged the app topped download charts overseas, including in African countries and distant islands in Oceania.
Alfred Sit Wing-han denied allegations the high number was mostly dubious and part of a coordinated bid to boost statistics.
He said over 97 percent of users had downloaded the app on Hong Kong phones, but said he was not surprised 2 to 3 percent happened abroad.
"Residents who study or work abroad could have downloaded the app from other countries," Sit said.
He added that download records are based on user locations and that it is impossible for a large number of foreigners to download a useless app.
According to the website Webfigures, it was the most frequently downloaded health and fitness app on Apple's App Store in 18 countries or regions over the past two weeks.
Hong Kong, Macau, and the mainland were among those areas, as well as Antigua and Barbuda, Belize, Bermuda, the Cayman Islands, and British overseas territories of Turks and Caicos, the Bahamas and the British Virgin Islands.
But the office of the government chief information officer said the number of downloads in eight of the above countries was zero, including Bermuda, the Bahamas and the Cayman Islands.