Two people died after a culvert along the SGR line collapsed in Mai Mahiu, Naivasha on Monday.
Four other workers were injured after they were buried in the culvert.
A worker who declined to be named said the section was weak following rains in the area over the past week.
He said they heard a loud bang, followed by screams as the section caved in and buried the workers.
"They were six and we managed to retrieve four who were rushed to hospital but the other two had died before we could rescue them," he said.
The worker said they victims did not have helmets or protective gear.
"Had the contractor provided safety gear, the lives would have been saved. We challenge the government to direct them to provide the same to us," he added.
Area OCS Ezra Sambu said the injured workers will be transfered to Kijabe Mission Hospital.
He said they are investigating the incident to establish if there was negligence.
The incident comes a week after 150 workers from the Pipeline camp downed their tools to protest risks associated with their job.
They said they are being forced to ride in open construction trucks, which they termed dangerous.
The contractors have now provided them with a mini bus.