Seven hundred ninety-six bodies of children were believed to be buried in a septic tank grave nearby an olden orphanage for children of unwed mothers in Tuam, Co Galway in Ireland.

The septic tank grave was first discovered 40 years ago with the government saying that the 271 children buried died because of famine that plagued the country.

However, local historian Catherine Corless found out that there were 796 bodies buried in the mass graveyard.

"I went to the births, deaths, marriages registration office in Galway and I asked them would they have records of the children who died at the home. When she came back to me, she said, 'We have the records ... but there's quite a number. I was staggered and I was shocked because there's a total number of 796 babies, children and toddlers buried in one mass grave there on that site, Corless told BBC.

Corless' discovery opens an inquiry to the already controversial Catholic Church.

In 1944, the government examined the graveyard and recorded 271 children bodies of children who all died of malnutrition. These children lived in the orphanage which also housed 61 unwed mothers, the Irish Examiner reports.

However, Corless discovered that death records of children showed other sickness, diseases, deformities and premature births as causes of deaths.

Elderly people living within the neighbourhood of the orphanage testified seeing the orphans going to school but were separated from other students. The children left the orphanage if they were adopted or if a church-run industry got them, unfortunately, for unpaid labour and abuse.

The true number of the buried bodies was kept secret as it reflected the 20th century Catholic teaching that involved out-of-wedlock children to be denied baptism and Christian burial. Unmarried mothers were detested both by the society and their families that their dead children were buried in unmarked graves in an open ground.

Corless's discovery implied that whoever was behind the conversion of the septic tank into a mass grave did it deliberately to deny these children of Catholic rites.

Out of respect for the 796 children buried, present Archbishop of Tuam Michael Neary said he will call on the Bon Secours Sisters, who ran the orphanage, to start a fundraising to build a monument for the children.

Corless, together with some activists, established the Children's Home Graveyard Committee and the group wanted more than just a monument. The group is calling for a state-funded investigation and excavation of the graveyard.

The government has yet to make a public statement about the issue.