The Prosecution had applied to hold State House digital strategist Dennis Itumbi for nine more days.
Itumbi appeared at Milimani Law Courts after the expiry of the five days granted to the DCI last week.
Itumbi was arrested last week on Wednesday in Nairobi's CBD over links to the fake assassination letter against Deputy President William Ruto.
On Thursday, the court allowed the police to detain him for five days after the prosecution requested 14 days to complete investigations.
Magistrate Zainab Abdul ordered five-day detention of the State House operative at Muthaiga police station.
"Fourteen days is too long a period since investigations already commenced on June 20. The respondent’s phone has also been confiscated for forensic examination," Abdul ruled.
In court last week, Itumbi sensationally claimed he has an audio and a video to prove there was a plot to assassinate Deputy President William Ruto.
He requested to play the recordings in court in camera, saying the investigators were aware he has them.
“I have an audio and video recording of material that could show, subject to investigations, that a meeting could have happened at a place called La Mada at which discussions were held on the possibility of the assassination of my employer, particularly the Deputy President," he said.
Lead investigator Yvonne Anyango said the allegations against Itumbi are a serious threat to national security and incitement to cause chaos in that can result in genocide.
Anyango further informed the court that they are investigating a serious criminal offence alleged to have been committed by the blogger and others still at large.
On July 1, Itumbi lashed out at the Daily Nation newspaper over an article he alleged indirectly and erroneously linked him to the letter.
The newspaper carried an article on Sunday which said two of Ruto's aides are being sought by the DCI on suspicion they circulated the letter. It said the two are from the communications department.
"They mentioned where the communication officers allegedly being sought work. We are about 10. None of us got a call or a text. Copy and paste journalism from unnamed sources who lie, should not find a home," Itumbi said.
Itumbi was taken to the DCI for questioning.
DCI officers investigating the letter by an unknown cabinet secretary have explored the theory that the alleged assassination plot could be a hoax.
The officers said they had traced the source of the letter and were about to summon those they suspect authored it.
"We are pretty confident that we are about to find those behind the letter. All we can tell you is that no cabinet secretary wrote the letter," one of the officers said.
