The police arrested five CPI(M) workers, including two local committee secretaries, in connection with the attack on a Kerala State Electricity Board (KSEB) office at Padur, near Alathur, on Tuesday.
The attack had been on those who reported for duty ignoring the trade union call for strike on Tuesday.
Those arrested were CPI(M) Padur local committee secretary Pramod Peechamkottil, 41; Kavassery local committee secretary Rajaneesh Kalarikkal, 35; Prasad Maruthampadam, 37; Radhakrishnan Thavakkal, 54; and Anoop Kunnumpuram, 28.
They reportedly surrendered before the police on Wednesday morning. They were produced before the Judicial First Class Magistrate Court at Alathur and were remanded in judicial custody for 15 days.
They were among a gang that attacked the KSEB office and its employees on Tuesday afternoon. Eight employees, including an assistant engineer, were injured in the attack and furniture and computers destroyed. The injured men were admitted to the District Hospital here.
Five of the victims of the CPI(M) attack had recently quit the CITU and joined INTUC. One of them was a BMS member, and two others were Left sympathisers.