Ambulance workers found 39 dead bodies, including one teenager, in the container of a truck parked at an industrial park in Purfleet, Essex, of the United Kingdom, according to CNN.
Police have arrested 25-year-old truck driver Morris Robinson of Northern Ireland on suspicion of murder. Paul Berry, the local councillor for Armagh in Northern Ireland, confirmed the driver's identity, although police are not commenting at this time.
Authorities believe the truck arrived by sea from the Belgian port city of Zeebrugge early Wednesday morning.
"Sickening news of 39 people found dead in a container in Grays," wrote Jackie Doyle-Price, the MP for the area in which the truck was found. "People trafficking is a vile and dangerous business. This is a big investigation for Essex Police. Let's hope they bring these murderers to justice."
Officials say the truck container was refrigerated, meaning temperatures could've been as low inside as -5 or -10 degrees Fahrenheit.
Police and the British Red Cross are working to identify the victims, including opening a hotline for anyone who believes a loved one may have been on the truck. The victims are not believed to be Bulgarian citizens, although the truck had been registered in Bulgaria in 2017, then left the country for good.
Critical to the investigation is tracking the route the truck traveled before the bodies were found in Essex, which police are now scrambling to do in order to gain more insight into who is responsible for the deaths.
According to the U.K.'s National Crime Agency, "the past year has seen increasing use of higher-risk methods of clandestine entry" including "movement of migrants (including children) into the U.K. in containers, refrigerated [heavy goods vehicles] and small boats, at a high risk to life of those migrants smuggled."
Nine people were found alive in a separate truck on a U.K. highway later Wednesday, and are receiving precautionary medical treatment before being turned over to immigration officers.