At least 13 people have been killed in an explosion at a firecracker factory in India's southern state of Kerala, officials say. The incident took place in Thrissur, where around 40 people were believed to be assembling firecrackers in a cluster of sheds for an upcoming festival. Several others were injured, with five reported to be in critical condition.

This was the second such incident this week. On Sunday, a blast at a firecracker factory in neighbouring Tamil Nadu state left at least 25 dead.

Accidental explosions are a grim routine in India's fireworks industry, recurring with troubling regularity - most visibly around Sivakasi in Tamil Nadu, which produces much of the country's supply.

The explosion in Thrissur on Tuesday around 15:30 local time triggered secondary blasts that slowed rescue efforts. Firecrackers were being made in temporary sheds near paddy fields with poor road access, hampering emergency response. The force of the blast was felt kilometres away - some residents mistook it for an earthquake - and nearby homes were damaged. Eyewitnesses described chaotic scenes as locals joined rescue efforts, pulling out the injured and dead.

Kerala's Revenue Minister K Rajan told the BBC that all fireworks units preparing for the upcoming Thrissur Pooram had permission to manufacture and store fireworks in designated areas. The workers were preparing fireworks for the Thiruvambady Temple, one of the two main participants in the climactic displays of the Thrissur Pooram.

Officials stated that food had been prepared for about 40 workers, suggesting at least that many were present when an explosion hit a shed. While municipal chairman PN Surendran attributed the blast to high afternoon temperatures, officials said the cause remains unclear. A magisterial inquiry has been ordered to establish what happened and fix responsibility.

Kerala Chief Minister Pinarayi Vijayan has announced that medical experts from other states will be brought to treat the burn victims if needed. Prime Minister Narendra Modi has also announced financial assistance of 200,000 rupees ($2,137) for the families of the deceased persons, and 50,000 rupees for those injured.

Firecracker factory accidents are common in India, where highly volatile chemicals are handled in cramped, low-cost setups where even a small spark can trigger explosions. The industry faces scrutiny over safety standards, with one study recording 9,896 accidents in the sector in Sivakasi between 2003 and 2010 alone, including 398 fatal incidents. In Kerala, a 2016 explosion at the Puttingal Temple in Kollam district killed more than 100 people and injured 400 more.