Police officers who responded to the hotel disco crush that killed three teenagers are to face investigation after it emerged they initially withdrew from the scene.
Chief Constable George Hamilton has referred the actions of the officers to the Police Ombudsman.
Three young people - Lauren Bullock (17), Connor Currie (16) and Morgan Barnard (17) - died following a crush near the entrance to the hotel in Cookstown on St Patrick's night.
Ombudsman Dr Michael Maguire is to examine how police responded when the first emergency call was made at around 9.30pm and will determine whether the response was appropriate.
A spokesman said: "Our thoughts are with the families who have been so tragically bereaved."
Explaining the referral to the Ombudsman, Deputy Chief Constable Stephen Martin said "it is right and proper that the actions of all those involved are considered". Describing the ongoing case as "active and wide-ranging", he explained that the first officers on the scene decided to withdraw after making an initial assessment.
When the first ambulance arrived police then moved forward in support of the emergency medical personnel.
"The timing and nature of police actions during this period require further investigation to fully establish the facts," Mr Martin insisted.
"The Chief Constable has therefore decided that the initial police response should be subject to independent scrutiny and it is in the public interest to refer the circumstances and the nature of the actions of the first officers arriving at the scene to the Police Ombudsman."
The families of the victims have been informed of the referral, he added.
"The confidence of the families and the confidence of the communities we serve are at the forefront of our minds in our decision to refer this matter to the Police Ombudsman," Mr Martin said. "We will work with the Ombudsman to support whatever action he undertakes and would ask that people do not speculate or prejudge the outcome of the Ombudsman's investigation."
The Police Ombudsman's Office issued an appeal for witnesses. "Our investigators have now begun gathering information about the initial sequence of events, and have appealed for witnesses to contact them," the spokesman said. "They are keen to hear from anyone who saw police in the area of the Greenvale Hotel on St Patrick's evening, March 17.
"Our investigators can be contacted by email at the following address: firstname.lastname@example.org."
Mid-Ulster MP Francie Molloy welcomed the Police Ombudsman's investigation and said the families of the teenagers have a "right to expect a full, thorough and comprehensive investigation".
"Families must have confidence in this investigative process and therefore the intervention of the Police Ombudsman is to be welcomed," he said.
Meanwhile, the Police Ombudsman's Office has said the PSNI's controversial handling of the arrest and subsequent "de-arrest" of Greenvale owner Michael McElhatton over a suspected drugs offence "will not form part" of its investigation.
Mr McElhatton, who was released on bail last week on suspicion of manslaughter in connection to the three teenagers' deaths, had been arrested last Wednesday on suspicion of possession of Class A drugs with intent to supply.
Two hours after the media was notified of the arrest, police revealed the 52-year-old had been "de-arrested" following forensic tests of a white powder seized from his home ruled out drugs.
Another man, aged 40, was also questioned on suspicion of manslaughter and released on bail pending further inquiries.
Mr McElhatton accused the PSNI of trying to "blacken" his name after his de-arrest for the drugs offence, prompting Detective Chief Superintendent Raymond Murray to defend the actions of investigating officers.
Speaking last Thursday, Mr Murray said releasing news of the arrest showed the PSNI's transparency in action, and if there had been a delay in the PSNI issuing the initial media update, officers would have been facing questions on why they were holding back information.
It has since emerged that politicians were invited to view an image of the white substance in question that same day at a PSNI station.
It was reported yesterday that the offer was turned down by SDLP councillor Denise Mullen, who told the Irish News that she was informed by the PSNI that other politicians had accepted the invite.