Indian police are questioning a man who surrendered after at least one homemade bomb exploded at a convention centre in Kerala state on Sunday where a Christian group was holding a prayer meeting, killing a woman and wounding dozens of others.

After initial questioning, the native of the city of Kochi, who surrendered in the southern state’s Thrissur district, will be interrogated in detail by a senior police official, Asianet News reported, citing sources.

The situation was under control and the police and other agencies were investigating it, Ernakulam District Collector N S K Umesh told Reuters.

“Investigation is taking its course, and we ensuring that everyone is getting the best medical treatment.”

The incident took place during a Jehovah’s Witnesses convention in Kalamassery, about 10 kilometres (6.21 miles) northeast of Kochi, and local media said over 2,000 people were in attendance over the three-day event.

Kerala’s health minister Veena George said a woman died at the scene while 52 others were hospitalised with injuries. Eighteen remained in intensive care unit, six of them in critical condition, including a 12-year-old girl.

Preliminary investigation showed that an improvised explosive device was used, Kerala Director General of Police Shaik Darvesh Saheb told reporters earlier.

Local newspaper Mathrubhumi, citing witnesses, said at least three explosions occurred inside the convention hall.

Asked if it was a terror attack, Saheb said he could confirm the details “only after investigating”.

Kerala Chief Minister Pinarayi Vijayan said the incident was unfortunate and the police were taking it very seriously.

Police were appointing a special investigations team, Saheb told reporters, adding that strict action would be taken against those involved.

An eight-member team from the National Security Guard, the Indian government’s counter-terrorism unit, was on its way to Kerala to investigate as well, media reported.

“The explosions occurred seconds after the end of a prayer as part of the day’s event. The first blast took place in the middle of the hall. Seconds later, two more explosions rocked simultaneously on either sides of the hall,” TA Sreekumar, regional spokesperson for the Jehovah’s Witnesses told mathrubhumi.com.

Jehovah’s Witnesses are an international Christian denomination founded in the United States around 1870. They are best known in many countries for door-to-door evangelism.

The group said it has about 60,000 followers in India.