London, October 23 (RHC)-- Police in southeastern England said at least 39 people were found dead Wednesday inside a truck container believed to have come from Bulgaria.  The truck, which is said to have entered Britain via the Welsh port of Holyhead several days ago, was found by ambulance workers at Waterglade Industrial Park, Grays.

"This is a tragic incident where a large number of people have lost their lives.  Our enquiries are ongoing to establish what has happened," Essex Police Chief Superintendent Andrew Mariner said.  "We are in the process of identifying the victims, however I anticipate that this could be a lengthy process."

A 25-year-old-man from Northern Ireland has been arrested on suspicion of murder and remains in custody.   A cordon has been put in place and access to and from the industrial park remains closed.

Prime Minister Boris Johnson said in a tweet he was appalled by what had happened and gave assurances that work was underway to find the cause of the incident.