Police in India are investigating a series of explosions which killed three people and injured more than 50 others in the southern state of Kerala.
The blasts took place during an event by Jehovah's Witnesses, a Christian-based religious movement, in the town of Kalamassery on Sunday.
A man was detained after he posted a video claiming responsibility for the attacks and surrendered to police.
Police said they were still trying to verify his confession.
"He is in our custody. He has also presented some pieces of evidence which we are verifying. The investigation is at its preliminary stage," Additional Director General of Police (Law and Order) MR Ajith Kumar told reporters.
The incident took place during a prayer session organised by Jehovah's Witnesses in Kalamassery. More than 2,000 followers were attending the three-day event.
Two people died on Sunday, while a 12-year-old girl with 95% burns succumbed to her injuries on Monday morning.
Senior police official Shaik Darvesh Saheb said a preliminary investigation indicated that an improvised explosive device (IED) placed inside a tiffin box might have caused the blasts.
Shortly after the incident, a man named Dominic Martin said he had carried out the attack.
The 48-year-old posted his confession in a Facebook video, which has since been deleted, and handed himself in at a nearby police station.
Mr Martin claimed he was a registered member of the religious group and was angry with its "anti-national" teachings.
But TA Sreekumar, a regional spokesperson for the Jehovah's Witnesses, has denied this and told Reuters that he was unaware if Mr Martin was even present at the event.
The Jehovah's Witnesses is a religious movement which believes that the traditional Christian churches have deviated from the actual teachings of the Bible and that the destruction of the world is imminent.
The group, which claims to have about 8.7 million followers worldwide, has a strong presence in Kerala and is known for their door-to-door evangelistic work in the state.
In 1986, its followers received a favourable verdict from India's Supreme Court against forcing their children to sing the national anthem in schools.
They argued that their conscience did not permit them to sing the anthem because it would constitute "a form of idolatry and an act of unfaithfulness to their Jehovah".
On Monday, Kerala Health Minister Veena George told reporters that 17 people had been admitted to different hospitals after the blasts, 12 of whom were in intensive care.
"Four are critically ill, three of them are on ventilators. Those who are critically ill have burns above 50-60%," she said.
Chief Minister Pinarayi Vijayan condemned the incident and announced that a 20-member team, led by the assistant director general of police, was investigating the incident.
He also held an an all-party meeting on Monday to discuss the blasts. Meanwhile, security has been tightened in India's capital Delhi and other cities like Mumbai in the wake of the blasts.