Police were given more time on Thursday to question a driver arrested on suspicion of murder after 39 people, believed to be Chinese nationals, were found dead in a refrigerated truck near London, with the investigation focusing on human trafficking.

Paramedics and police found the bodies of 31 men and eight women on Wednesday in a truck container on an industrial estate at Grays in Essex, about 20 miles (30 km) east of London.

The National Crime Agency, which targets serious and organised crime, said it was helping the investigation and working urgently to identify any gangs involved.