Only one out of the four cases in which EACC wanted governors dragged to court this week over alleged corruption is solid.
Director of Public Prosecutions Noordin Haji on Wednesday said only one governor was likely to face prosecution.
Mr Haji told the Senate legal affairs committee that his office had returned the other three files to the anti-corruption commission to fill gaps.
The chief public prosecutor, however, did not name the targeted governors, saying it would jeopardise investigations.
"All the 57 files we received from EACC were returned on Monday," he said.
"(For) some, we have asked them to proceed with prosecutions and others we have asked them to address the gaps."
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He told the senators that his office is still in consultation with EACC over some high-profile cases.
He said most of the cases involve corruption of amounts ranging between Sh5,000 and Sh10,000.
In others, he said they had recommended administrative action, without giving details.
Last week EACC CEO Halakhe Waqo told the same committee that they had a watertight cases against four governors and that the county bosses will be arraigned this week.
He said EACC had carried out investigations for one year and they have enough evidence.