Story highlights Investigators uncovered human remains in what may have been a sewage treatment facility

Tests indicate the remains are of individuals ranging in age from 35 weeks' gestation to 3 years

(CNN) Excavations have uncovered "significant quantities of human remains" at a former home for unmarried mothers run by nuns in Ireland, officials said Friday. Tests indicated they belonged to young children.

The remains were found in the chambers of an underground structure next to a septic tank which could have been used for sewage storage or treatment, the Commission on Mother and Baby Homes said in a statement Friday.

"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," the statement said.

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The institution, which operated from 1925 to 1961, was run by the Sisters of Bon Secours. Its former site is now part of a housing estate.

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