DUBLIN — The government and the police are coming under increasing pressure to open an investigation into allegations that a Roman Catholic religious order secretly buried up to 796 babies and toddlers born to unmarried mothers in a septic tank over several decades.

Speaking in the Irish Parliament on Wednesday, the minister for Children and Youth Affairs, Charlie Flanagan, called the discovery of what is described as an unmarked grave as “deeply disturbing and a shocking reminder of a darker past in Ireland when our children were not cherished as they should have been.”

The burials are believed to have taken place on the site of a so-called mother-and-baby home in Tuam, County Galway, from 1925 to 1961. The institution, which was run by the Sisters of Bon Secours, was subsequently demolished, and a housing development now sits adjacent to the site.

The Sisters have declined to comment. They were reported to be meeting with the local bishop. They have neither denied nor confirmed the practice.