DPP Noordin Haji has asked Inspector General of Police Joseph Boinnet to investigate the insurance company that covered the bus that killed 58 people in a fatal accident at Fort Ternan a month ago.
The October 10 accident also left 15 other people critically injured.
The DPP also wants Boinnet to direct police investigators to establish whether the body builder observed set specifications.
"Once the investigations are complete, do forward the file to us immediately for appropriate directions," Haji said in a statement on Thursday.
The bus owner Bernard Ishindu Shitiabayi and the Sacco administrator Cleophas Shimanyula (alias Toto) were arrested and charged over the accident.
NTSA confirmed that the bus, KBX 029 J, was not registered with the authority.
NTSA Director General Francis Meja also said the bus was not licenced to operate at night although it had a valid insurance.
Shitiabayi faced three charges: allowing the bus to operate without a speed governor, operating the bus at night without a night travel license and failing to register the names of the driver and conductor of the bus.
Shimanyula faced the last two charges.
The duo was charged on October 22 at the Narok Court where they pleaded not guilty to the charges.
They were both released on a bond of Sh5 million with a surety of a similar amount or cash bail of Sh1 million in the alternative.
The hearing of the case is scheduled for November 28.