Three of the six suspected terrorists arrested in Shella, Malindi, on Friday have been detained for 30 days to allow the police to complete their investigations.
The suspects appeared in court Monday but were not charged after the investigating officer, Ali Bakari, asked Malindi Chief Magistrate Julie Oseko for more time to conclude investigations.
Those who appeared in court were Abdirahim Salim Mohamed, Salim Abdulkarim Salim and Nur Swaleh Mahdi.
Malindi police boss Matawa Muchangi said the other three suspects, who are university students, had been released.
In a sworn affidavit, Mr Bakari said officers from the Directorate of Criminal Investigations wanted to establish if the suspects were members of a terror group.
They also want to establish if they were involved in soliciting for and giving support to a terrorist group.
Bakari told the court he had information the suspects were financing members of Al Shabaab. He said the suspects were also planning an attack in Malindi prior to their arrest.
"We are extending our investigations to Ethiopia, Somalia, Mombasa, Malindi and Lamu," said Bakari.
The officer said he also needed time to investigate a Malindi-based forex bureau in connection with the alleged offences.
"I need more time because of the nature of the investigations and the areas I need to cover. I also need to take their mobile phones and laptops to Nairobi for analysis and get their call data records for forensic tests," said Bakari.
"I fear the respondents may go out of the jurisdiction of this court before the investigations are complete if this application is not allowed. The investigations cannot be completed within 24 hours."
The suspects, represented by lawyer Patrick Shujaa, opposed the application, arguing 30 days was too long for them to be detained.
The magistrate granted the application and directed the suspects held at Malindi Police Station.