The driver of the tour bus in which 26 people died when it crashed into a barrier and caught on fire in Taiwan on July 19 was drunk when the accident occurred, investigators said on Friday.

In the worst road accident ever to overcome Chinese mainland visitors to the island, the entire tour group of 23 tourists and a guide were killed as they headed for Taiwan Taoyuan International Airport to return home. The driver and another tour guide from Taiwan also died in the crash.

Investigators said tests done on the driver, identified only by his surname Su, revealed his blood-alcohol level was 215 mg per 100 ml, more than four times the legal limit.

"He was drunken driving, a very severe case of drunken driving," said Wang Yi-wen, chief investigator and deputy chief prosecutor of the Taoyuan District Prosecutors Office.

Investigators are trying to determine what role the driver's intoxication may have played in the accident.

An Fengshan, a spokesman with the Taiwan Affairs Office of the State Council, said in a statement on Friday that the mainland has paid close attention to the investigation results disclosed by Taiwan authorities.

"We have repeatedly asked the Taiwan authorities to investigate the cause of the accident, who was responsible, and to console the victims and their family members," he said.

A memorial service was held on Friday morning in Dalian, Liaoning province, where most of the victims came from.

Zhang Qing, 48, said her younger sister, Zhang Hong, died along with her husband, child and mother-in-law in the accident.

Relatives of the tourists went with a work team in charge of the accident to Taiwan to identify the dead, and they returned home with their cremated remains on Tuesday.

The team said that relatives of 23 victims have agreed to sign a compensation contract made by Taiwan, and the other decided to deal to seek legal recourse.