A man has died a day after being arrested in a joint anti-drugs operation by the police and customs in Yuen Long, officers said on Thursday.

The force said the man, 57, was one of four people arrested on Wednesday in connection with the discovery of drugs worth HK$100 million in a container from South America.

"During the investigation, the man suddenly struggled violently and tried to drive away. Three police officers who were present at the time immediately restrained the man. In the process, the three officers were injured," said Chan Kong-ming, a senior superintendent from the Narcotics Bureau.

Chan said the suspect was then handcuffed in his car.

"Around 20 minutes later, the man suddenly fell unconscious. Our police officers immediately asked for support and gave him emergency treatment at the scene."

He died in hospital on Thursday.

Police said an initial investigation showed that the man wasn't injured before the struggle, and that he had a history of heart disease.

The other arrestees were charged with a drugs trafficking offence and were due to appear in Fanling Magistrates' Courts on Friday.