PRESCOTT, Ont. -- A Chinese tourist, who was among 24 people injured when a bus drove off the highway in eastern Ontario on Monday, has died, provincial police said.

The 54-year-old man was pronounced dead in hospital, officers said Tuesday morning. Four other passengers are still in critical, life-threatening condition in hospital.

The tour bus carrying 37 people -- the driver, a guide and 35 Chinese tourists -- was between the communities of Brockville and Prescott when it went off Highway 401 and hit a rock formation by the side of the road.

OPP are still investigating what led to the crash, Const. Suzanne Runciman said.

"It's going to take some time to investigate," Runciman added. "There's lots of witnesses to talk to and ... there's mechanical things they need to took into so it's going to take some time before we can tell you the cause."

Officials from the Chinese embassy in Ottawa, about 100 km north of the crash site, have visited injured passengers in hospital and have been in touch with their families, spokesperson Yang Yundong said in a written statement.

Chinese diplomats in Canada have "made clear that the travel agency involved should shoulder its responsibility and properly take care of such matters as medical treatment and compensation for the Chinese tourists," Chinese Foreign Ministry spokesperson Hua Chunying told a press conference Tuesday, a transcript of which was posted to the embassy's website.

"The Foreign Ministry and our diplomatic missions in Canada will continue to follow the development of the accident and work with relevant departments to make proper followup arrangements," Chunying added.

A manager at the Massachusetts-based Union Tour Express company said Monday he was aware one of their buses was involved in the collision but could not provide any further information about the incident.

Ontario Provincial Police will not release the name of the deceased passenger until his family has been notified, though the man's loved ones can also request not to have his identity made public, Runciman said. collision.