The team investigating the killing of radical Muslim cleric Sheikh Aboud Rogo has been given more time to conclude the matter.
The Director of Public Prosecutions (DPP) Keriako Tobiko also transformed the team into a task force in what he said would give it more powers to effectively deliver on its mandate.
The task force would now be required to hand in its report within two months.
Three weeks ago, Sheikh Rogo, who was accused of funding terrorist groups, was gunned down in Mombasa as he drove his wife to hospital.
The incident sparked angry protests from his supporters leading to several deaths, plunder and destruction of property.
Mr Tobiko subsequently formed a team drawn from the police, Kenya National Commission on Human Rights, Law Society of Kenya and the Independent Police Oversight Authority to investigate the killings.
On Wednesday, the investigators handed in their preliminary report but indicated that the two-week period they had been given was not sufficient to complete the probe.
Jacob Ondari, the convener of the team, also reported that they faced logistical challenges in doing their work.
Mr Tobiko’s decision to change the group into a task force comes after civil society groups demanded that it be given more powers to investigate other recent mysterious killings in Kenya.
The group, under the umbrella name of Kenyans for Peace with Truth and Justice (KPTJ), last week demanded that the government investigates all cases in which individuals previously charged in court with crimes related terrorism have either died or disappeared.
“We note with concern the increase of forced disappearances and extra-judicial killings of Kenyans,” said Kenya Human Rights Commission Executive Director Atsango Chesoni.
“We demand that the mandate of the taskforce be extended to investigate the disappearances of other Kenyans.”