The pigs had been dead for seven hours. But scientists noted that their hearts, livers and kidneys were still showing signs of life.
Within minutes of the final heartbeat, a lack of blood flow, oxygen, and nutrients triggers a cascade of biochemical events that begins to destroy a body's cells and organs.
So how were the pigs' organs performing certain functions so long after their final breath?
Researchers at Yale School of Medicine in the US used a new technology that delivers a specially designed cell-protective fluid.
The cutting edge technique meant they were able to restore blood circulation and other cellular functions in the pigs a full hour after their deaths, with many functions observed up to seven hours later.
The findings may help extend the health of human organs during surgery and expand availability of donor organs, the authors of the study published in the journal Nature said.
"All cells do not die immediately, there is a more protracted series of events," said David Andrijevic, associate research scientist in neuroscience at Yale School of Medicine and co-lead author of the study.
"It is a process in which you can intervene, stop, and restore some cellular function."
In a study that may sound a bit like science-fiction, cardiac arrest was induced in anaesthetised pigs, which were then treated with OrganEx an hour after death.
Six hours after treatment with OrganEx, the scientists found that certain key cellular functions were active in many areas of the pigs' bodies - including in the heart, liver, and kidneys - and that some organ function had been restored.
For instance, they found evidence of electrical activity in the heart, which retained the ability to contract.
"We were also able to restore circulation throughout the body, which amazed us," Nenad Sestan, the Harvey and Kate Cushing professor of neuroscience and professor of comparative medicine, genetics, and psychiatry said.
Normally, when the heart stops beating, organs begin to swell, collapsing blood vessels and blocking circulation, he said.
Yet, circulation was restored and organs in the deceased pigs that received OrganEx treatment appeared functional at the level of cells and tissue.
"Under the microscope, it was difficult to tell the difference between a healthy organ and one which had been treated with OrganEx technology after death," Zvonimir Vrselja, associate research scientist, said.
The researchers stressed that additional studies are necessary to understand the apparently restored motor functions in the animals, and that rigorous ethical review from other scientists and bioethicists is required.
The OrganEx technology could eventually have several potential applications, the authors said.
For instance, it could extend the life of organs in human patients and expand the availability of donor organs for transplant.
It might also be able to help treat organs or tissue damaged by ischemia during heart attacks or strokes.