At least 36 people were killed at a quarry at Koromei in Mandera County on Tuesday morning by suspected Al-Shabaab militants.
All the victims were non-Muslims and most of them are said to be hailing from Chaka in Kiganjo, Nyeri County.
Some survivors have told the police that Muslims, who were at the site, were spared.
The victims were made to line up and most of them were shot on the head while some were beheaded.
Police say they were attacked as they were sleeping in tents at the site at around 1am.
The Inspector General of Police David Kimaiyo said that they were attacked at a quarry in Koromei, about 10 km from Mandera town.