The parents of the two children who were last week found dead in a car at Athi River police station after missing for three weeks are among the chief suspects.
Sleuths from the Directorate of Criminal Investigations visited the scene twice and questioned several people, including a man who works at the police canteen who said he had seen the two children in the yard.
Sources said DCI officers are closely following leads, which link the disappearance of the two children to one of the couples.
Police, according to the source, suspect that the parents could be linked to a cult and might have been involved in the matter based on two strange things officers found on the bodies of the children.
The officers said they noted the strange manner in which the children's bodies were arranged in the legroom of the rear seats and the fact that the boy was naked and his clothes were missing.
Initial investigations reveal that the deaths could be linked to an occult practice, a clue that has seen detectives focus on the parents as they could have planned the killings.
Several people have provided information that links the couple to the disappearance.
One source alleged that the killing could have been a "sacrifice deal" that required a firstborn and a last-born child.
It is suspected that the parents could have sacrificed the children to acquire riches and must have offered their own child and any other.
"There is crucial information which makes detectives believe the couple has a case to answer. From preliminary investigations into the cruel death, the incident might not have just been cruelty but a heinous act targeting a beneficial outcome," said the source.