A mass grave containing “significant quantities" of infants' remains has been discovered at a former Catholic mother and baby home in western Ireland.

The discovery, announced by investigators Friday, follows a probe by a historian in 2014 who found the death certificates for nearly 800 children who died at the home in Tuam, County Galway, between its opening in 1925 and closure in 1961.

The government-appointed Mother and Baby Homes Commission said the remains were found in at least 17 of 20 underground chambers during excavations between November and February. The chambers appeared to be related to the treatment of sewage or waste water, it said.

A small number of the remains of up to 35-week-old fetuses, and babies and toddlers aged up to 3, were taken for analysis.

The commission said radiocarbon dating of the samples suggested the remains were from the time when the home operated, and further tests were being carried out.

“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.”

Katherine Zappone, Ireland's minister for children and youth affairs, said the news, which confirmed long-standing rumors, was “sad and disturbing,” although not unexpected.

“Today is about remembering and respecting the dignity of the children who lived their short lives in this Home. We will honour their memory and make sure that we take the right actions now to treat their remains appropriately," she said in a statement.

The Bon Secours sisters, the religious order of nuns who ran the home, said they had no comment to make about the investigation.

"The Bon Secours sisters are fully committed to the work of the Commission regarding the mother and baby home in Tuam. On the closing of the Home in 1961 all the records for the Home were returned to Galway County Council who are the owners and occupiers of the lands of the Home. We can therefore make no comment on today’s announcement, other than to confirm our continued cooperation with and support for the work of the Commission in seeking the truth about the home," the order said in a statement carried by thejournal.ie.