Hong Kong, China (CNN) -- Typhoon Megi advanced in Asia on Friday, triggering rock slides that trapped more than 400 people in automobiles in Taiwan, officials said.
A tour bus was stuck on a cliff, with the driver and a passenger suspected still trapped inside, according to the Coast Guard Administration of Taiwan. It was not immediately clear whether they were injured or dead. Another tour bus, with 19 people aboard, was missing.
Soldiers were deployed to rescue those trapped, including about 200 visitors from China, said Cai Min, a spokesman for Taiwan's National Disaster Prevention and Protection Commission. More than two dozen travelers had been rescued by late afternoon Friday, officials said.
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The rock slides happened mainly along the Suhua Highway, in northeast Taiwan, Cai said.
No deaths or serious injuries were immediately reported, however.
Megi, which killed at least 11 people in the Philippines, is expected to reach southern China early Saturday, according to the Hong Kong Observatory.
As of late afternoon Friday, Megi was estimated at about 430 kilometers (267 miles) east of Hong Kong. Winds were estimated at 41 to 62 kilometers per hour (25 to 39 miles per hour).
On the streets of Hong Kong, there were still no signs of the typhoon, though.
"Although it is difficult to predict Megi's exact track, the public should stay alert and attend to their personal safety. They should stay away from the shoreline, avoid unnecessary outdoor activities and ensure drains are not blocked," acting Secretary for Security Lai Tung-kwok said.
As precautions, crews in Hong Kong were deployed to pile sandbags, inspect and trim trees and check drains. Temporary shelters were being opened, and myriad boats were moored.
Megi may be the strongest typhoon to hit China this year, the state-run Xinhua news agency has said.
In southern China, strong gales arrived ahead of Megi. Domestic and international flights have been cancelled, and ferry services have been suspended in Guangdong, Fujian and Hainan, state-run China Daily said.
In Guangdong, crews have fanned out to inspect reservoirs, dikes and water-conservation projects, in an effort to prevent storm-related injuries and deaths.
Nearly 130,000 fishing boats have been recalled in Fujian, Guangdong and Hainan provinces, and more than 150,000 people have fled for safety in Fujian, according to Xinhua.
Officials have issued the highest of four warnings, bracing for possible devastation in coastal areas, Xinhua said. The warning allows local officials six hours to evacuate residents, close schools and airports, and recall vessels that are considered at risk.
On Thursday in the Philippines, lawmakers placed the province of Pangasinan under a state of emergency, to help municipalities recover from Megi, which was known in the Philippines as Typhoon Juan.
The typhoon affected an estimated 258,844 Filipinos, leaving thousands homeless.
CNN's Helena Hong contributed to this report.