KUALA LUMPUR (AFP) - A horrific bus crash in Thailand left four members of the same family dead, it was reported on Monday (Dec 21).

The four victims spanned three generations, including an 85- year-old grandmother and her 39-year-old granddaughter, according to the The Star newspaper in Malaysia.

"We are all in shock," a relative of the family in Malaysia was quoted as saying by The Star. Two members of the family survived the accident.

Some 22 Malaysians, mostly elderly, had gone to Chiang Mai on December 17 for a five-day tour organised by Malaysian tour operator Chiu Travel.

The accident occurred on Sunday (Dec 20) in Doi Saket district 30 kilometres from the northern city of Chiang Mai. The accident killed 13 Malaysian tourists and injured several others.

Chiu Travel manager Terence Yung told AFP that the company had flown 15 Malaysian relatives of victims to Thailand and they were expected to reach Chiang Mai on Monday evening to help identify bodies.

Thai police said a total of 14 people were killed in the accident, 13 Malaysians and one Thai. Malaysia's foreign ministry and Chiu Travel confirmed the number of Malaysians killed in the crash as 13. Chiu Travel said one Thai tour guide was also killed.

Images posted online by local news outlets showed scene of devastation as rescuers battled to reach those trapped inside the smashed bus, which had come to rest in thick foliage with its roof caved in.

Some of those still inside had suffered severe injuries. In one picture, seven parts of white sheeting had been draped to cover either bodies or body parts.

Yung said his company was still trying to find out how the accident happened but said, based on information he had received from Thailand, the crash was a result of the driver trying to overtake another vehicle.

"The only way we can stop these accidents is for the tour leader to ensure the local (Thai) drivers don't drive recklessly," he said.

Prime Minister Najib Razak expressed sadness on his Facebook page.

"I am saddened to hear news of the accident in Chiang Mai where 13 Malaysians died and express my condolences to the victims' families," he wrote.

"The government would ensure every effort is made in bringing home the victims' bodies and help the victims' families."