Krishnamurthy and Senthil, an engineering department official arrested along with the former minister, were on Sunday produced before a judge who remanded them to 15 days' judicial custody.
The former minister was summoned for questioning by CB-CID and arrested late last night, a senior CB-CID official said.
Krishnamurthy was sacked as a minister recently in the wake of the political row over the death of Muthukumarasamy, who allegedly committed suicide 44 days back because of alleged pressure from the minister while recruiting seven drivers.
Krishnamurthy and Senthil were on Sunday taken to Tirunelveli where they were produced before Judicial Magistrate Senthil Kumar at his residence.
They were remanded to 15 days' judicial custody and sent to Palyamkottai central prison in Tirunelveli, the police sources said.
On February 20, Muthukurmarasamy allegedly jumped in front of a train and died.
Soon after, allegations were made by opposition parties including Paattali Makkal Katchi, Congress, Dravida Munnetra Kazhagam that the official killed himself 'due to pressure' of Krishnamurthy and sought his arrest and a CBI probe.
The death of the official snowballed into a political row prompting All India Anna Dravida Munnetra Kazhagam to drop Krishnamurthy from the state cabinet and strip him off his party posts.
Commenting on the arrest, DMK spokesman T K S Elangovan said it had come too late.
He maintained that the case must be probed by CBI as the opposition party has lost faith in CB-CIB of state police.
"There should a proper probe... Only CBI can bring out the truth," he said, adding that he did not have faith in CB-CID as Krishnamurthy was a minister in the state.