The wife and father of Mahir Khalid Rizik, the suicide terrorist who blew himself at Dusit D2 hotel on Tuesday, have been arrested.
A police source said the two are being flown to Nairobi by officers from the Anti-Terror Police Unit for interrogations.
The wife, Sahaila Mwinyi, was nabbed at Bakarani, Kisauni.
The father whose identity is yet to be established was arrested at Majengo, Mvita.
The arrests come after five suspects in the attack that left 21 dead were arraigned on Friday.
They five were; Joel Nganga, Oliver Muthee, Gladys Kaari, Guleid Abdihakim and Osman Ibrahim.
The state applied to have the suspects detained for 30 days to enable detectives to conclude the investigations.
Two of the suspects were arrested on Wednesday soon after the 20-hour siege came to an end following the killing of all five terrorists.
The Director of Criminal Investigations George Kinoti said on Wednesday the suspects were arrested in Eastleigh and Ruaka estates.
He said they were being treated as the key suspects because they were in contact with the terrorists.
Detectives are also pursuing Violet Kemunto, the wife of one of the suspects.
Investigators said they found bomb-making material at the house of one of the suspects in Mucatha, Kiambu county.