HALIFAX, Nova Scotia (AP) – Conjoined twin baby girls from Liberia who were traveling to New York for medical treatment died aboard a plane that was diverted to Halifax on Thursday.

Royal Canadian Mounted Police Cpl. Joe Taplin said the Delta Air Lines flight was about 35 minutes from the Nova Scotia coast when the girls’ mother noticed the 1-month-old infants had stopped breathing.

“A medical doctor on board gave medical assistance, but the twins were pronounced dead when they arrived at Stanfield International Airport,” Taplin said.

Peter Spurway, spokesman for the airport, said the call came in around 1 p.m. local time, and the plane landed without incident shortly after.

Taplin said the twins were headed to New York to undergo treatment for an unspecified illness. There were no other details on the cause of death.

Passengers sitting near the twins were also interviewed before the plane, which originated in Brussels, resumed its trip to New York’s John F. Kennedy International Airport, Taplin said.