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 (10:00 GMT) triggered secondary blasts that slowed rescue efforts. Firecrackers were being made in temporary sheds near paddy fields with poor road access, hampering emergency response.


Eyewitnesses described chaotic scenes as locals joined rescue efforts, pulling out the injured and dead. Kerala's Revenue Minister K Rajan asserted that all fireworks units preparing for the upcoming Thrissur Pooram - a major annual Hindu temple festival - had permission to manufacture and store fireworks in designated areas.


Officials reported that food had been prepared for about 40 workers, suggesting at least that many were present when the explosion hit a shed.


The blast's force was felt kilometres away, with some residents mistaking it for an earthquake, damaging nearby homes. While municipal chairman PN Surendran attributed the blast to high afternoon temperatures, officials said the cause remains unclear.


Prime Minister Narendra Modi expressed condolences, announcing financial assistance of 200,000 rupees ($2,137; £1,582) for the families of the deceased and 50,000 rupees for those injured. A magisterial inquiry has been ordered to uncover the cause of this tragic event.


Firecracker factory accidents are common in India due to the highly volatile chemicals handled in cramped, low-cost setups where even a small spark can trigger explosions. This industry faces repeated scrutiny over safety standards, especially during festival seasons like Diwali.