The Police Ombudsman is to assess the case of a 39-year-old woman who died in Newry while waiting 45 minutes for an ambulance crew to arrive.
The PSNI advised Police Omdusman Marie Anderson about the matter because officers were with Jody Keenan shortly before she died.
Ms Keenan died in the early hours of Sunday after collapsing in the Trevor Hill area of Newry, Co Down.
The ambulance service received an emergency call at approximately 3.15am but due to a shortage of available crews, no ambulance was available in the area.
Instead a PSNI officers were the first to arrive at 3.52am but Ms Keenan died despite attempts to resuscitate her.
Her mother rushed to the scene and performed CPR.
Newry, Mourne and Down PSNI district commander Superintendent Norman Haslett said the Ombudsman office was contacted because police were with Jody shortly before her death.
"We are currently assisting the ombudsman with their assessment and our thoughts remain firmly at this time with Jody's family, friends, colleagues and all those affected by this tragic incident.
"Whilst the Police Ombudsman conducts her assessment no further comment will be made."
The Northern Ireland Ambulance Service (NIAS) has said a serious incident review will be carried out.
At the time Ms Keenan collapsed, there were only two ambulance crews available in the Southern division. On a Saturday night, the planned number of available crews is 10.
Both available crews in the Southern division area were at Craigavon hospital handing over patients.
Instead, after the Ambulance service received the call about Ms Keenan, an ambulance was sent from Belfast, 38 miles away. A second ambulance was then sent from Banbridge.
The vehicle from Banbridge arrived at 4.03am, 48 minutes after the 999 appeal was made. The ambulance from Belfast arrived at 4.15.
A Police Ombudsman spokesman added: “The Police Ombudsman has been notified of this incident by the PSNI and preliminary inquiries are underway. The Ombudsman cannot comment further at this stage.”