Detectives in Nyamira have vowed to nab the killers of a US-based couple ahead of their burial on Friday.

They were killed at their Nyamakoroto home in Kitutu Masaba

The bodies of Edward Nyagechi and his wife Grace Morema were found in separate parts of their residential complex with machete cuts.

On Monday, Keroka subcounty police commander Robert Ndambiri said they were still chasing useful leads which could potentially lead to the arrest and subsequent arraignment of the key suspects.

"It's not a matter of if but when. They would all be in custody very soon," Ndambiri told the Star in Keroka.

He said they will pounce on the suspect ahead of the couple's burial on Friday.

The couple were visiting their village from the USA on March 21 before killers stormed into their house at night and killed them.

Nyagechi was found dead in his garage with deep cuts to his head.

He had his hands and legs bound with a binding wire.

His wife Grace Morema, 60, was found in the bedroom with deep cuts to the neck.

She was also tied up similarly to her husband.

A domestic staffer and a farm hand are already in custody to aid in investigations.

Ndambiri said they are already using important leads gleaned from their interrogation to unravel the murder.