A middle-aged man died at a quarry in Katani Village in Athi River sub county on Thursday.
Benjamin Wanjala had visited the site with a hired truck to pick ballast he had paid for.
Mlolongo Assistant County Commissioner Obed Mose who addressed the press at his office in Mlolongo town said the deceased died under unclear circumstances.
"The deceased who was accompanied by the truck's driver Michael Omondi had gone to the quarry to pick "Kokoto" he paid for at the site's main entrance before the driver took the truck to the loading zone," said Mose.
He said Wanjala disappeared immediately the truck was parked at the zone and was being loaded by a shovel.
He said the driver started looking for the deceased when he noticed that he had mysteriously disappeared from his sight.
Mose said out of suspicion, the driver ordered the loading shovel's operator to offload the ballast he had loaded on the truck, only to find Wanjala's lifeless body in the truck.
He said the operator loaded the truck without knowing that the deceased was inside it, leading to his death.
Mose said the body was moved to Machakos Level Five Hospital mortuary and that police had launched investigations in to the matter.