At least 18 people were killed and more than 40 injured in Thailand Sunday when a freight train crashed into a bus taking passengers to a religious ceremony, officials said.

The morning collision, around 50 kilometres (30 miles) east of the capital, Bangkok, toppled the bus and sheared off part of its roof.

More than 40 passengers were rushed to nearby medical facilities for treatment, said provincial hospital director Sombat Chutimanukul.

“Four are in critical condition and eight remain under observation” out of the 23 admitted to her hospital, she told reporters.

By late afternoon, more than 30 passengers who had sustained mild injuries were sent home, said a local police chief.

“The death toll is at 18,” he told AFP, adding that “the investigation on the cause of the accident is ongoing”.

Footage shared by a government department showed the bus edging from the road onto train tracks before a blue cargo train slammed into its side.

“I was frozen in fear when I saw the crash… It was a terrible sight,” said Pitchitra Thongwichit, 34, who lives close to the tracks.

“All the passengers were moaning and crying for help.”