Conjoined twins in Malawi have died prior to a surgery that was meant to separate them. The boys who were born over a week ago were scheduled to be operated on, but died prior to the procedure due to a blood shortage, Malawi24 reported Thursday.

A spokesperson for the Kamuzu Central Hospital in Lilongwe where the twins were supposed to be operated on confirmed the deaths of the newborns. The twins who were connected at the heart and liver were supposed to be surgically separated Wednesday but the procedure was delayed due to a shortage in their blood group.

For the procedure to take place, the hospital needed about 200ml of all negative blood, however, due to a lack of it, the twins died from lung complications, BBC reported. “I am very depressed. They had a high chance of survival despite being born prematurely and I was optimistic the procedure would go well, but then, there are things we have no control over,” lead surgeon Dr. Carlos Valera said.

The operation was expected to last a minimum of three hours and consist of a team of four doctors and several other hospital personnel. The hospital has a history of successfully separating conjoined twins, and expectations were high prior to the operation. Several citizens even took to social media to send well wishes to the team and twins.

The Malawi-born twins were not the only ones who required separation. In early October, conjoined twins from Illinois, Jadon and Anias McDonald were successfully separated following a long and arduous surgery, ABC 7 NY reported. An operation of this magnitude consists of several risks, including long-term brain damage and possibly death for one or both of the children.

Jadon and Anias were 13 months at the time of their surgery. The boys who were joined at the head are classified as craniopagus twins. The chance of birthing craniopagus twins is one out of 2.5 million. One-third die within 24 hours following birth.