The 39 migrants who died in the back of a refrigerated truck in England last week left bloody handprints on the inside doors of the metal container.

Many of the victims in the gruesome pile of bodies were either naked or partially clothed, and some had foam around their mouths, according to The Sun newspaper.

Police are still trying to identify the victims — 38 adults, including 31 men, seven women and one teenage girl — a task made harder because they were likely human trafficking victims who traveled through several countries before they climbed into the container in Brussels to reach England.

It is now thought the majority of the victims were from Vietnam, not China, as originally believed, Reuters reported. It’s possible that some or all of them had traveled through China and may have had false Chinese passports. China said it could not yet confirm the victims’ nationalities or identities.

The family of a 26-year-old woman who is believed to be among the victims said they paid about $38,000 for her to be smuggled to the U.K. through China. Pham Thi Tra My texted a series of messages to her family that she was suffocating in the truck and apologized that her journey ended tragically. “I’m sorry Mom, my path to abroad didn’t succeed,” My wrote about 10:30 p.m. Tuesday. “Mom, I love you and Dad so much! I’m dying because I can’t breathe,” she added.

The U.K.-based organization VietHome said it sent the pictures of nearly 20 people reported missing to the police. Many of the victims are thought to be from the same small village in Vietnam.

British police are questioning four suspects, including a man detained at an airport on Friday on suspicion of manslaughter and conspiracy to traffic people, along with a couple from Warrington, about 20 miles east of Liverpool. The truck driver, who is from Northern Ireland, was arrested at the scene where the bodies were found. He was said to be “horrified” when he saw the mass of bodies, and was the one who called the police.