"Tell all I'll see them on the other side," read the note found with the body of 51-year-old mine foreman Martin Toler Jr. "It wasn't bad. I just went to sleep. I love you Jr."
The notes have shifted the focus of the families, reports CBS News correspondent Sharyn Alfonsi. At first the families were angry about how they learned the rescue attempt had failed.
"The more I think about it, the more I wonder if they couldn't have moved a little faster," said Peggy Cohen, daughter or miner Fred Ware.
J. Davitt McAteer, an expert in mining safety, told Alfonsi the equipment for the rescue teams in the United States is 30 to 40 years old, and the communication systems are 25 to 35 years old.
"The time it took to get the teams in place, the time it took to get the equipment there, the time it took to activate it raises some questions about whether our rescue system is sufficient in this country today," McAteer said.
Federal investigators are now trying to determine if the rescue was botched, Alfonsi reports.
The miners died after an explosion that rocked the mine Monday morning. Eleven of the victims were discovered nearly 42 hours after the blast, at the deepest point of the mine, behind a curtain-like barrier set up to keep out carbon monoxide, a toxic byproduct of combustion that was found to be present at deadly levels inside the shaft. The 12th victim was believed to have been killed by the blast itself.
Autopsies were under way Thursday, and officials would not comment on the cause of death or how long the men might have survived.
Tom Toler, Martin's older brother who worked 30 years in the mine with him, said Thursday that the note was "written very lightly and very loosely" in block letters on the back of an insurance application form his brother had in his pocket.
"I took it to mean that it was written in the final stages," the brother said. "I'd call it more or less scribbling."
John Groves, whose brother Jerry was one of the victims, told The Associated Press that he knew that at least four notes were left behind. He said his family did not receive one.
No note was found on the body of 59-year-old machine operator Fred Ware Jr., but Cohen said she and other relatives who went to identify bodies at a temporary morgue were told by the medical examiner that some of the men wrote letters with a similar message: "Your dad didn't suffer."
"The notes said they weren't suffering, they were just going to sleep," said Cohen, who planned to retrieve her father's belongings to see if he had put such a note in his lunch box.
Cohen said her father had the peaceful look of someone who died of carbon monoxide, and the only mark on his body was a bruise on his chest.
"It comforts me to know he didn't suffer and he wasn't bruised or crushed," she said. "I didn't need a note. I think I needed to visualize and see him."