Eyewitnesses said the bridge collapsed due to the weight of the lorry and its load.
The sugar miller confirmed one of their lorries was on the bridge and was headed to Homa Bay to deliver sugarcane.
Take a quick survey and help us improve our website!Take a survey
"Four years ago, we restricted our drivers from using that bridge," Sukari Industries said in a statement.
"We have launched an investigation to establish why the driver decided to go against the company's directive."
The miller added it was working closely with the local community and leaders from the region to get a solution.