Denison, Iowa ? Dozens of residents attended a memorial service in a drizzly dusk to pray for the souls of 11 unidentified adults who perished in a stifling grain hopper, apparently while attempting to sneak into the United States.

Their bodies barely more than huddled skeletons were discovered here earlier this week when the Union Pacific hopper that entombed them was opened for a routine cleaning after four months in storage in Oklahoma.

After a full day of autopsies in Des Moines, the state medical examiner determined that seven of the dead were men and four were women. The official cause of death: Overheating and dehydration. Beyond that, there are few facts. Only horrible conjecture.

“Such a very slow, very sad, very awful death,” said Nadia Castanela, 27. She pulled her toddler son close.

“I came to ask God that they have peace.”

Thousands of illegal immigrants from Mexico and Central America hide themselves in freight trains each year in a dangerous gamble to push north. Most often, they are guided into cars by a smuggler, or coyote, who may charge several hundred or even several thousand dollars for his services. Few bring along food or water.

Parishioners at St. Rose of Lima Catholic Church participate in a memorial service in Denison, Iowa. The memorial Wednesday was for the 11 people whose badly decomposed bodies were found this week in a rail car at a grain elevator in Denison.

“Usually the smuggler knows where the train is going and gets someone there to meet it and unlock the car,” said Julio Salinas, a supervisor with the Border Patrol’s office in McAllen, Tex. “But, as in this case, it doesn’t always happen.”

At Wednesday’s memorial at St. Rose of Lima Catholic Church, a choir sang. A dozen candles flickered in an alcove by the altar.

Off in the corner, 17-year-old Aaron Espino prayed.

“When I see the trains now,” he said, “I think of them. I think there could be people in there. There could be people in there dying.”