Thousands of bodies were left to decay at a donation center at Paris-Descartes University, leading to an investigation from the school.

An investigation from L’Express newspaper published Tuesday revealed that dozens of bodies were left to decompose on tables in what was described as a “mass grave,” and alleged some body parts were sold to private companies, BBC reported.

Some bodies were stacked on top of each other, and others had been gnawed by mice in the building, the report alleges. The practices detailed in the investigation had gone on for more than a decade, BBC reports.

The University of Paris-Descartes released a statement on Wednesday, acknowledging the reports from L’Express and apologizing to the families of the deceased. The school said it would conduct an investigation to ensure the body donation system had proper conditions.

“These measures will establish the reality of the facts and the way forward to consider reopening the site in the best conditions,” the university said in a statement.

Following the investigation published by L’Express, The French Union for Free Medicine (UFML) told France Info it would file a complaint against the university’s center.

Jerome Mary, president of the UFML, said the report showed an attack on the “dignity and integrity of the person,” which he called “a shame.”