The explosion was apparently set off when two men were testing equipment.

Selangor police chief Noor Azam Jamaluddin told reporters that a team of officers from the North Klang Narcotics Criminal Investigation Division found “precursor” materials used to process methamphetamine.

The materials and equipment were able to produce RM1.8 million worth of meth, he added.

They included meth oil, able to produce 18.5kg of meth, and 5kg of liquid meth.

Azam said two local men had been detained.

“One of the suspects, aged 47, is unemployed and has three criminal records, mostly for drugs. He was detained after an illegal drug lab was discovered in Mantin in 2016 but was released after trial.

“The other, aged 52, has three previous convictions for drug offences. He was arrested in China in 2007 and jailed for 10 years,” he said.

Azam said these two men were brought together by a third person, who police are trying to trace.

The two suspects have been remanded until Oct 18.

“This is the fourth drug lab uncovered in Selangor this year,” Azam said.