The stringent Unlawful Activities (Prevention) Act has been invoked in the case relating to a car explosion in the city that killed one person, while five others have been arrested over the incident and police have intensified the probe covering all aspects including terror angle.

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

With some of them being enquired by the National Investigation Agency (NIA) in 2019, the police were also probing their activities after that, City Police Commissioner V Balakrishnan said.

Hours after the Tamil Nadu BJP questioned why the police had not specified the reasons for the arrest of the five and the sections under which they have been detained, Balakrishnan said that besides the UAPA, other IPC sections like conspiracy have also been included in the case.

Police are also probing if the man killed in the gas cylinder explosion in the car on Sunday, 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, 75 kg 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 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 has been invoked since there was an explosion.."all angles are being probed," he said.

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

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

Meanwhile, theopposition 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," TN BJP president K Annamalai said, addressing a press conference in Chennai.

The DMK came to power winning the 2021 elections and chief minister M K Stalin holds the Home portfolio. After the DMK came to power, the priorities have changed, he indicated.

Annamalai expressed apprehensions if the Sunday explosion was some kind of 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."

Without divulging details, he said he has written to Union Home Minister Amit Shah over the explosion.

In an apparent response to Annamalai, state Minister V Senthil Balaji said following the incident, steps were taken to ensure peaceful Deepavali celebrations in the city.

"On the directions of the CM, the DGP visited the spot after the incident. Arrests were made and the police and the government acted diligently (following which), there was no flutter among people, he said in a tweet.

The Electricity Minister alleged some people wanted to gain "political mileage" over possible "communal riots" but that would not happen in Tamil Nadu.