Assam Director General of Police Mukesh Sahay told PTI that Rajarshi Sen Deka had allegedly got a job in the state civil services through "unfair means".
With this, the number of serving civil service officials arrested in the last six days in connection with the scam has gone up to 22, he said.
The officers are accused of paying money for getting jobs in the elite services. "After evading arrest for some days, Rajarshi today surrendered (to the police) and we arrested him," he added.
Without sharing details, Sahay said more arrests were expected in the next few days. "It appears that one official is evading arrest and is out of the state," he said.
Nilamani Sen Deka was the Agriculture Minister in the erstwhile Congress government of Tarun Gogoi and was defeated in the 2016 state assembly poll.
The police had identified 25 civil service officials of the 2015 batch appointed by the Assam Public Service Commission (APSC) in the scam and had their answer scripts checked by forensic experts, which confirmed anomalies.
Of them, 13 are from the Assam Civil Services, seven from the Assam Police Services and the rest from the allied civil services.
On November 8, in a surprise operation, the police arrested 16 civil service officials allegedly involved in the scam.
Former chairman APSC Rakesh Kumar Paul was arrested on November 4 last year and Rs 50 lakh seized from him. Some 'benami' properties belonging to him were also identified.
Two APSC members Samedur Rahman and Basanta Kumar Doley were arrested later.
It was followed by the arrest of APSC Assistant Controller of Examinations Pabitra Kaibarta. Some more officials and others were later arrested in connection with the scam.