A 56-year-old man is being investigated in South Korea on suspicion of starting a deadly wildfire that killed 30 people.

The man, who has not been named, was performing an ancestral rite by a family grave on a hill in Uiseong county, North Gyeongsang province, at the time.

He has been booked – but not arrested – and will be called in for questioning once the investigation of the site has been completed. He denies the charges.

On Sunday, officials said the main fire had finally been brought under complete control – 10 days after it started, causing widespread damage to buildings, including historic temples.

Investigators reportedly spoke to the suspect’s daughter, who is said to have told them that the fire began as her father tried to burn tree branches hanging over the graves with a cigarette lighter.

The fires subsequently burned more than 48,000 hectares – equivalent to about 80% of the area of the capital, Seoul – according to the Korea Forest Service.

They also destroyed an estimated 4,000 structures, including homes, factories and a number of national treasures.

Goun Temple – a Unesco World Heritage Site – was among the structures destroyed in the blaze. It was built in AD618 and was one of the largest in the province.

Most of the casualties were people in their 60s and 70s.

Even though the main fire has been brought under control, smaller ones continue to reignite, authorities say.

Fuelled by strong and dry winds, the fires spread to several cities and counties.

Unseasonably warm weather, dry conditions and pine forests in the region also helped exacerbate the fires.

An investigation involving the police, fire authorities and forest management will be carried out next week.

South Korea’s acting President Han Duck-soo said the government would provide financial support for those who had been displaced by the fires.