The Unlawful Activities (Prevention) Act has been invoked against the accused in Sunday’s car explosion that killed one person, Coimbatore police revealed on Tuesday, hours after announcing the arrest of five people for the crime.

The arrested were identified by the police as Muhammad Talka, Muhammed Azharuddin, Muhammed Riyaz, Firoze Ismail and Muhammed Nawaz Ismail, all in their 20s.

The National Investigation Agency had questioned some of the arrested persons in 2019. The police are also probing their activities after that, city police commissioner V. Balakrishnan said.

Balakrishnan said that besides the UAPA, IPC sections including that of conspiracy had been invoked.

The Tamil Nadu BJP had earlier asked why the police had not specified the reasons for the arrest of the five and the sections under which they had been detained.

The police are also probing if the man killed in the gas cylinder explosion in the car, Jemisha Mubeen, had any links with Mohammed Azharuddin, an accused in the Easter Sunday bomb blasts in a Sri Lankan Church in 2019, which killed over 250 people. The Kerala visits of the some of the arrested are also being investigated.

Further, 75kg of potassium nitrate, charcoal and aluminium powder have been recovered from Mubeen’s house, Balakrishnan added. These chemicals are used in making country bombs, police had said earlier.

“UAPA has been invoked since there has been an explosion,” Balakrishnan told reporters here.

Three of the arrested were seen in a CCTV footage, along with Mubeen earlier, carrying two LPG cylinders and two small drums, the content of which has been sent for forensic examination, the police commissioner said.

While the three had helped Mubeen carry the items “with knowledge”, another person was apprehended for coordination. One man was arrested for providing the car, Balakrishnan added.

Asked if the police were probing a possible terror angle, Balakrishnan reiterated that the UAPA had been invoked since there was an explosion. “All angles are being probed," he added.

Soon after the explosion on Sunday, the police took steps to maintain law and order and this ensured Diwali was celebrated peacefully on Monday, he said.

The number of checkposts in the city have been increased and pickets erected wherever required.

Opposition BJP targeted the ruling DMK over the matter and said it exposed “intelligence failure”.

“How long will it take for the chief minister to accept the intelligence has failed... bring professionals back to the force... the home department had solid professionals, with those good in counter-terrorism, prior to 2021,” Tamil Nadu BJP president K. Annamalai told reporters in Chennai. The DMK came to power after winning the 2021 elections and chief minister M.K. Stalin holds the home portfolio.

Annamalai expressed apprehensions about the Sunday explosion being a “suicide attack”, and claimed the western region of the state, comprising the industrial city of Coimbatore among others, was in the radar of “the ISIS”.