The glitch came on a day when several firms announced earnings, preventing investors from accessing company announcements made during the midday break. HKEx said that in order to give investors time to get the price-sensitive information elsewhere, it decided to adopt a half day (i.e. one trading session) suspension policy for firms announcing results during the lunch publication window on Wednesday.

According to Li at a news conference held Wednesday afternoon, eight companies were affected including HSBC, Cathay Pacific, Dah Sing Bank, China Power, and HKEx, all of which announced interim results during the midday break.

"Our current assessment is that the glitch could be the result of an external attack," said Li. "HKEx is now investigating the problem and the HKEx news website services will resume as soon as the technical problem is resolved."