DMK president M Karunanidhi's son and party treasurer M K Stalin was on Saturday detained by police for staging a road roko in neighbouring Tiruvarur district.
Police said Stalin, former deputy chief minister, and some of his aides were picked up after they squatted on the road when the police wanted to question Tiruvarur DMK district secretary Kalalichelvan in connection with a case.
Top district police officials said Stalin was likely to be "let-off" later.
Police said a case had been registered against Kalaichelvan for allegedly preventing students of a school in Koradacheri, about 30 km from Tiruvarur, from attending their classes on Friday as part of DMK's boycott call over uniform education system, now pending before Supreme Court.
As the students were returning home after being allegedly 'forced out' by the DMK men, a student died in a road accident involving the bus in which he was travelling.
Stalin came to Koradacheri on Saturday to express his condolences to the family of the boy and was accompanied by Kalaichelvan and DMK MP A K S Vijayan.
When police sought to take into custody Kalaichelvan, the DMK men led by Stalin resorted to a road roko leading to their detention.
Shops downed their shutters in Tiruvarur while about 150 DMK men were taken into custody in Thanjavur when they protested against the detention of Stalin, police said.
Chief minister J Jayalalithaa on Friday blamed the DMK protest for leading to the death of the boy and charged Kalaichelvan with instigating his party workers to prevent students from attending classes.
"I strongly condemn the DMK protest which was responsible for the death of Vijay," she had said in a statement announcing a cash relief of Rs two lakh to his kin.