A teenager travelling in a luxury car being chased by police was killed when it crashed with a car driven by a nun.
Conal Daly, 18, from greater Belfast was one of three males travelling in the Jaguar Sovereign last night when it collided with the elderly nun's Volkswagen Polo on the Saintfield Road between Belfast and Carryduff.
Both the nun and one of the survivors from the Jaguar are in a critical condition in the Royal Victoria Hospital.
The other male is in a stable condition.
As police were pursuing the vehicle at the time, in line with procedures the incident has been referred to the Police Ombudsman.
The PSNI is also conducting its own investigation into the crash, which happened around 8.40pm.
A spokesman from the Ombudsman's Office appealed for witnesses to come forward.
"We would be keen to speak to anyone who saw the collision or the pursuit leading up to it," he said.
"We understand the pursuit began close to the roundabout at the junction of the Ravenhill Road and Ormeau Road in Belfast."
The incident is the second serious road crash involving nuns in three weeks.
At the end of September Belfast nuns Sister Marie Duddy and Sister Frances Forde were killed on the outskirts of Newry when the car they were travelling in collided with a police car.
Three policemen suffered minor injuries in the collision.
The Police Ombudsman is also investigating that crash.
Last night the Saintfield Road was closed between the Manse Road and Ivanhoe Avenue.
The accident happened as widespread flooding sparked havoc on Northern Ireland's roads, with torrential downpours causing excess surface water.
DUP councillor Jack Beattie, the Mayor of Castlereagh, said his heart goes out to those involved in the accident.
He added: "It's not just that the road carries a lot of traffic, but it's probably been due to the fact that it's been dry and the roads have been saturated tonight. It (the road) is a death trap." He added: "There are too many accidents on that road."
Local Alliance councillor Geraldine Rice said: "It is a really bad night, but the thing that worries me is that there are a lot of accidents on that road and when there is heavy rain that road is prone to flooding.
"I hope that this wasn't anything to do with it.
"If there has been a fatality, our thoughts and prayers are with the family.
"We will be following it up with the police and the Department of Regional Development (DRD)."
The accident came just a day after Northern Ireland's roads claimed the lives of two teenagers, taking this year's death toll to 65.
That grim total compares to 57 for the whole of 2013.
Enda Dolan was struck by a van in south Belfast close to Elms student village.
The 18-year-old Omagh native had just moved to the city to study architecture at Queen's University.
In a crash in Coleraine, Emma Scott (17) was killed after the Mini she was driving was involved in a collision.
The collision happened at Creamery Road shortly after 11am.