The first train was traveling from the Zhejiang provincial capital of Hangzhou when it lost power in the lightning strike and was hit from behind by the second train in Wenzhou city at 8:27 p.m. (1230 GMT), the official Xinhua News Agency said.
The provincial emergency office told Xinhua that at least 32 people were killed and 191 injured.
A preliminary investigation by the Zhejiang provincial government released early Sunday showed that four coaches of the moving train fell off the viaduct, Xinhua said. The cars plunged about 65 to 100 feet (20 to 30 meters) from the elevated section of track, Xinhua said.
Photos taken at the scene showed one badly damaged car lying on its side by the viaduct and another car leaning against the viaduct after landing on its end..
Xinhua quoted an unidentified witness as saying "rescuers have dragged many passengers out of the coach that fell on the ground."
Minister of Railways Sheng Guangzu, who was heading to the accident scene, ordered an in-depth investigation of the accident.
The trains involved are "D'' trains, the first generation bullet train with an average speed of about 95 miles (150 kilometers) per hour and not as fast as the new Beijing-Shanghai line.
Xinhua said the train hit by lightning was "D3115." It said the Ministry of Railways confirmed that it was hit from behind by train "D301."
China has spent billions of dollars and plans more massive spending to link the country with a high-speed rail network. Recently, power outages and other malfunctions have plagued the showcase high-speed line between Beijing and Shanghai since it opened on June 30.
Official plans call for China's bullet train network to expand to 8,000 miles (13,000 kilometers) of track this year and 10,000 miles (16,000 kilometers) by 2020.
The huge spending connected with the rail expansion also has been blamed for corruption, and Railways Minister Liu Zhijun was dismissed this spring amid an investigation into unspecified corruption allegations.
No details have been released about the allegations against him, but news reports say they include kickbacks, bribes, illegal contracts and sexual liaisons.