A "significant" number of baby remains have been unearthed at a former home for unmarried mothers and their babies.
The discovery was made in several underground chambers located below a disused Catholic Church institution in Tuam, County Galway.
A commission, tasked with investigating alleged abuse at religious-run so-called mother and baby homes, had been excavating the site in west Ireland.
Remains were found in at least 17 of the 20 excavated chambers, according to the commission.
Spokespeople involved in the excavation said they were "shocked" at the discovery made beneath the home, which operated from 1925 to 1961.
The remains found involved a number of individuals, with age-at-death ranges from approximately 35 foetal weeks to two-to-three years.
"Radiocarbon dating of the samples recovered suggest that the remains date from the time frame relevant to the operation of the mother and baby home," a spokesperson for Commission of Investigation into Mother and Baby Homes said.
A number of the samples are likely to date from the 1950s, the commission added.
"The Commission is shocked by this discovery and is continuing its investigation into who was responsible for the disposal of human remains in this way," it said in a statement.
"Meanwhile, the commission has asked that the relevant State authorities take responsibility for the appropriate treatment of the remains."
A coroner has been notified of the findings.
Ireland's Children's Minister Katherine Zappone TD described the discovery as "very sad and disturbing news."
"It was not unexpected as there were claims about human remains on the site over the last number of years," she said.
The commission, set up two years ago, was charged with investigating high mortality rates at mother and baby homes across several decades of the 20th century, the burial practices at these sites and also secret and illegal adoptions and vaccine trials on children.
It is thought about 35,000 unmarried mothers spent time in one of 10 homes run by religious orders in Ireland.
An inquiry was ordered after massive national and international focus on the story of the Sisters of the Bon Secours in Tuam, where the remains of 796 infants are believed to be buried.