Officials confirmed Thursday foreigners were among the 37 people killed when a bus crashed in Malaysia's worst-ever road accident, as reports said the vehicle was overloaded and had been banned from roads.

The express bus had 53 aboard when it veered off a busy and treacherous mountain road Wednesday, tumbling into a deep gully and scattering dead and injured on the mountainside.

The dead included 14 Malaysians, a Korean, one Nepalese, and a Bangladeshi-born Canadian passport-holder, said health ministry official Jeya Indran Sinnadurai.

The rest were yet to be identified, he told reporters.

Sixteen survivors are in hospital, including Malaysian, Indonesian, Bangladeshi and Thai nationals. Jeya said all were expected to pull through.

"All those who were critical, we have been able to turn around," he said.

Housing and Urban Wellbeing Minister Abdul Rahman Dahlan was quoted as saying the vehicle's capacity was 44.

"You do the math," Rahman told reporters when asked if the bus was overloaded.

The bus plied an express line bringing visitors to the Genting Highlands resort, a mountaintop gambling and entertainment park near the capital Kuala Lumpur.

Leading daily The Star said the vehicle had previously been "blacklisted" by authorities, but it did not say why and AFP could not verify the claim.

Survivors said the bus's brakes appeared to fail before it swerved off the road and down a steep 70-metre (230-foot) hillside.

"It kept picking up speed and everyone was screaming in fear... There was a lorry in front and the bus driver had to swerve to avoid it and lost control," passenger Suriardi Budiarto was quoted saying by the Star.

He survived because he was flung clear of the bus.

The tragedy is certain to bring new scrutiny on the notoriously steep and winding road serving the resort, which is popular with Malaysians and foreigners.

The route has seen several accidents over the years.

Two Indian tourists died and 22 people were hurt when a bus overturned last year. Seventeen people died in 1996 when their bus veered off the road.

The resort's casino and amusement park draw about 20 million visitors a year. It is undergoing a major refurbishment that will include construction of a Twentieth Century Fox theme park set to open in 2016.

The resort is operated by Resorts World Genting, which is owned by Genting Malaysia, one of the country's largest companies.

Resorts World Genting expressed "sadness" over the accident but stressed in a statement that it does not operate the bus line.

"That road is very dangerous, with too many curves. They should make it smoother. Even without touching the accelerator you can end up crashing," Ong Cheng Hoe, 54, told AFP.

Ong's brother-in-law Lim Kok Hoe, 43, was the bus driver. He was among those killed.

In ordering an investigation of the crash, Deputy Prime Minister Muhyiddin Yassin called for greater attention to safety on the Genting route.

"The Genting Highlands road is a very important route used by many tourists on a daily basis, thus the enforcement of all relevant laws must be given priority to ensure it remains safe," The Star quoted him saying.