Police said the Eritrean inmates had all been illegal immigrants.
The discovery last month of mutilated female bodies wrapped in plastic bags horrified Kenyans and cast further scrutiny on the performance of the country’s police force.
The dead were all women aged 18 to 30 and the murders are alleged to have taken place between 2022 and last month.
Jumaisi was arrested soon after the bodies were discovered, when police raided a bar where he had been watching the Euro 2024 final.
Mohamed Amin, head of the Directorate of Criminal Investigations, said at the time: “We are dealing with a serial killer, a psychopathic serial killer who has no respect for human life.
“The suspect confessed to have lured, killed and disposed of 42 female bodies at the dumping site.”
Police said they had found 10 phones at his home, along with a laptop, identity cards, female clothing and a machete officers believe was used to chop up victims.
It is the second time in barely six months that a suspect in a high-profile case has escaped from custody.
Kenyan national Kevin Kangethe, who is accused of murdering his girlfriend in the United States last year and leaving her body in an airport car park, fled a police station in February before being caught about a week later.