LONDON • All 39 people found dead in a refrigerated container truck near an English port were Chinese citizens, British police confirmed Thursday as they investigated one of the country’s deadliest cases of people smuggling.

The Essex Police force said 31 men and eight women were found dead in the truck early Wednesday at an industrial park in Grays, a town 25 miles east of London.

A magistrate gave detectives another 24 hours to question the driver, a 25-year-old man from Northern Ireland who has been arrested on suspicion of attempted murder.

He has not been charged, and police have not released his name.

Police in Northern Ireland searched three properties there as detectives sought to piece together how the truck’s cab, its container and the victims came together on such a deadly journey.

Pippa Mills, deputy chief of Essex Police, said the process of conducting post-mortem examinations and identifying the victims would be “lengthy and complex.”

“This is an incredibly sensitive and high-profile investigation, and we are working swiftly to gather as full a picture as possible as to how these people lost their lives,” she said.

The Chinese Foreign Ministry said Chinese Embassy employees in the U.K. were driving to the scene of the crime to aid the investigation.

Signs and candles on a wall were placed at a vigil Thursday for the 39 truck victims outside the Home Office in London.

the associated press