BANGKOK — At least 20 people have died following an explosion at a fireworks depot in central Thailand, according to officials.

People were also injured in the incident, the Department of Disaster Prevention and Mitigation said, but it did not say how many.

Officials were working to secure the site in Suphan Buri province and help people who were impacted, the department said.

Suphan Buri is about 60 miles northwest of Bangkok, in the heart of Thailand's central rice-growing region.

It was not immediately clear what caused the explosion, which happened at around 4 p.m. local time (4 a.m. ET) on Wednesday in Suphan Buri province, north of Thailand’s capital Bangkok, local police said.

“We estimated there are about 10 deaths, we are still investigating the cause and the exact number of casualties,” Police Col. Peerapoj Rawangbarn told CNN earlier.

Khaosod newspaper quoted local residents saying around 30 workers had been in the factory.

Police said the fire around the area had now been put out, and that rescue workers and forensic officers were working to retrieve human remains from and around the demolished factory.

Firework accidents are not uncommon in Thailand. At least 12 people were killed and 121 injured in an explosion in July last year at a fireworks warehouse in the southern village of Mu No. More than 100 houses were damaged in the blast.

Prime Minister Srettha Thavisin was briefed on the explosion while he was at the World Economic Forum in Davos, Switzerland, and ordered an urgent investigation to see if the explosion was caused by negligence, Reuters reported.

“The prime minister ordered an inspection of the plant to see if it was operating legally and if the explosion was caused by negligence.

“The law must be enforced to the fullest extent because there are innocent deaths and injuries,” his office said.

Photos posted on social media showed a thick plume of black smoke rising over the scene of the blast in an otherwise unoccupied rice field. Photos posted online by local rescue workers showed the factory site virtually leveled flat aside from debris and body parts.

National police chief Torsak Sukvimol confirmed local news reports that there had been another explosion at the factory in November last year that killed one worker and seriously injured three others.

The blast, the cause of which was not immediately clear, came less than a month before Chinese New Year in February, when demand for fireworks is strong. — Agencies