Koibatra was taken into custody from his house and his interrogation was on, police said.
Police searched a flat in the name of Paul's wife and seized 11 APSC answer scripts, nine marks tabulation scripts, Rs 10 lakh in cash, a laptop and three mobile phones.
Following the arrest of APSC Chairman on November 4, its Member Samedur Rahman, who had been absconding, was arrested on November 9 from Rangia near Guwahati.
Patir was arrested on October 27 following a complaint filed by a dental surgeon that he had promised to give her a job through the APSC for a bribe of Rs 10 lakh.
More From This Section
The Assam government at a Cabinet meeting on November 9 adopted a proposal to approach the state Governor for suspension of APSC Chairman Rakesh Kumar Paul.
On November 7, CID sleuths had sealed three rooms, including confidential room and answer script storing strong room, in the APSC headquarters office in Guwahati.
APSC has been mired in controversies with allegations of corruption in selection and appointment of Assam Civil Service (ACS), Assam Police Service (APS), Education Service, allied services and all gazetted posts for exchange of hefty amounts of money.