Three accused have been arrested and efforts are on to nab another person who is at large, Parliamentary Affairs Minister Bikram Keshari Arukh said in a statement.
Investigation into the case has been handed over to the crime branch police, he said in the Assembly.
The minister's statement came after Speaker Niranjan Pujari had on Saturday directed the state government to make a statement on Sahu's killing on January 26 at Niali area of Cuttack district.
He said Kartik had earlier been convicted and imprisoned in another murder case and was allegedly involved in five other serious cases.
The Assembly had witnessed pandemonium on Saturday with opposition Congress demanding a statement from Chief Minister Naveen Patnaik on Sahu's killing, alleging that the state government was trying to shield the culprits.
Sahu, also a farmer, had sought information regarding cultivation in Niali area. Therefore, he was killed and his body buried, he said.