The four were identified as Alok Das, Jagadish Bag, Santosh Rana and Naresh Singh alias Pental from Bolangir district, Additional Director General of Police, Crime Branch, B K Sharma told reporters here.
While attributing the motive to business rivalry between Alok Das and the Sahu, Sharma did not rule out the possibility of political rivalry being a factor as well.
"We have not paid much attention to that (political) angle as yet. But we will continue to probe further," he said replying to a question.
Sahu said on December 15, finding him alone the conspirators used a car to hit him and when he fell down slit his throat.
A breakthrough was made from Sahu's calls on his mobile phone and CCTV footage from a camera in front of a hotel, he added.
Sahu was the General Secretary of BJD's youth wing and a member of the state executive committee of the party.