At least 50 people were killed in a bus crash between Nairobi and Kenya's western city of Kisumu on Wednesday, police told the Daily Nation, and President Uhuru Kenyatta said authorities were investigating what he called a catastrophic incident.
Witnesses said the bus swerved off the road while driving down a steep slope, the newspaper said.
Reuters could not immediately reach a police spokesman to confirm the toll.
Kenyatta said the authorities were investigating the cause of the accident.
"As authorities investigate the cause of the accident with a view of taking action, I would like to remind drivers to always exercise caution to avoid such catastrophic incident," he said on Twitter.
"My heartfelt condolences to the families of fellow Kenyans who lost their lives in a tragic road accident at Fort Ternan in Kericho County this morning and wish those in hospital quick recovery."
(With inputs from agencies.)