Landslides caused by the typhoon killed nine people and buried a Buddhist temple in hardest hit Ilan county in Taiwan's northeast, where a record 45 inches (114 centimeters) of rain fell over 48 hours.
Two other people drowned in their flooded homes in Ilan, the Central Emergency Operations Center said. A total of 23 people were missing.
Megi earlier killed 26 people and damaged homes and crops in the Philippines.
The storm was expected to come ashore midday Saturday in China's Fujian province. Authorities have already evacuated 272,300 people from villages, according to the provincial water resources department.
News footage from Fujian showed waves crashing on the shore amid steady rain, and residents have used rope to secure street lamps and other objects that could be blown away by the wind. Workers tied down large boats in the Zhangpu port a few hours before the typhoon was expected to hit.
In Taiwan, Transport Minister Mao Chih-kuo said rescuers found parts of a mangled vehicle believed to have carried the missing Chinese tourists at a deep valley next to the coastal highway that winds through the forested mountains in Ilan.
"The bus was covered all over by thick mud," Mao said.
Next to the vehicle was the wreckage of another bus crushed by a huge boulder, but an unspecified number of Chinese tourists on that bus had narrowly escaped, Mao added.
Several buses carrying Chinese tourists were on a 6-mile (10-kilometer) stretch of the Ilan coastal highway that was hit by at least seven rockslides Thursday night. A 500-yard (500-meter) stretch of the highway had collapsed.
Nineteen Chinese on another bus were rescued, but the Taiwanese driver and the Chinese tour guide were still missing, officials said. The rescued travelers told reporters the driver and the guide helped them get to safety before a boulder crushed the bus and sent them down a valley with the vehicle.
The rockslides trapped 30 buses, cars and vans, stranding a total of 400 people. All other stranded travelers had been rescued by early Saturday, Interior Minister Chiang Yi-hua said.
Earlier this week, Megi killed more than two dozen people and damaged thousands of homes in the northern Philippines. The storm also forced 55,000 Filipinos from their homes and caused about $175 million in damage to infrastructure and crops, disaster officials said.
In Fujian, more than 53,000 fishing boats have been ordered to dock, and authorities were taking steps to prevent fishermen from returning without permission. Rescuers were on alert with hundreds of buses and trucks at their disposal, and crews were prepared to fan out to repair damaged roads.
In Vietnam, the death toll from severe flooding in four central provinces climbed to 75, including 14 victims from a bus swept off a road by strong currents, with six passengers still missing, disaster officials said Friday.
While Megi bypassed Vietnam, the country's central region was pummeled by 4.6 feet (140 centimeters) of rain over the past week, inundating large swaths of land, submerging nearly 280,000 houses and forcing more than 170,000 villagers from their homes.
Meanwhile, another storm, Cyclone Giri, was spinning in the Bay of Bengal and likely to make landfall Saturday in western Myanmar. The storm was expected to hit with winds of 75 mph (120 kph) and a tidal surge as high as 12 feet (370 centimeters).
