LONDON (AP) — Police in southeastern England say 39 people were found dead in a truck container believed to have come from Bulgaria.

A 25-year-old-man from Northern Ireland has been arrested on suspicion of murder.  

Chief Superintendent Andrew Mariner said Wednesday that authorities are in the process of trying to identify the 38 adults and one teenager. It is expected to be a lengthy process.

Mariner says the truck entered the country on Saturday, Oct. 19 and that police were "working closely with our partners to investigate."  

A cordon has been put in place around Waterglade Industrial Park in Thurrock, which remains closed.