The remains of at least 15,500 aborted and miscarried babies were incinerated as clinical waste and even used to heat some hospitals in the United Kingdom, an investigation has revealed.

The Department of Health on Sunday issued an instant ban after 10National Health Service trusts admitted to burning fetal remains alongside garbage and two others used the remains in “waste-to-energy” programs, the U.K. Telegraph reported.

“Dispatches,” an investigative news program on the U.K. television station Channel 4, revealed that at least 15,500 fetal remains were incinerated by 27 NHS trusts over the last two years.

Addenbrooke’s Hospital in Cambridge incinerated 797 babies in its “waste to energy program,” while telling mothers the remains had been “cremated,” the Telegraph said.

And Ipswich Hospital incinerated 1,101 fetal remains brought in from another hospital to generate energy between 2011 and 2013.

“This practice is totally unacceptable,” said Health Minister Dr. Dan Poulter. “While the vast majority of hospitals are acting in the appropriate way, that must be the case for all hospitals and the Human Tissue Authority has now been asked to ensure that it acts on this issue without delay.”

The NHS Medical Director, Sir Bruce Keogh, has written to all NHStrusts to tell them to immediately halt the practice.

The Chief Medical Officer has also written to the Human Tissue Authority to review its policies, the Telegraph reported.