PSNI chiefs will be questioned by the Policing Board about why they were apparently unprepared for Rangers fans' celebrations to descend into a potential Covid-19 super-spreader event.
Crowds of hundreds of men, women and children were pictured on west Belfast's Shankill Road on Sunday night celebrating the victory, but there was no sign of a police presence, with reports officers had been "advised to avoid" the area.
The PSNI said yesterday the "street party" scenes, which saw street drinking and fireworks released, were "clearly a breach of the Health Protection (Coronavirus) Regulations".
Superintendent Nigel Henry said officers "received reports... about large numbers of people celebrating in the Shankill Road area", but gave no details of any deployments.
He said police were also "aware of fireworks being let off" there and at Ballysillan Road in north Belfast.
"The numbers involved in the scenes last night were clearly a breach of the Health Protection (Coronavirus) Regulations, which is so disappointing when we know so many other people are adhering to the regulations and playing their part to keep people safe.
"An investigation is under way, and appropriate enforcement action will be taken in relation to breaches of the regulations."
The PSNI did not confirm if police ground units were advised to avoid the Shankill Road area on Sunday night or reports there were not enough officers available to enter the area.
There was also no detail given of what, if any, evidence was gathered on Sunday night by officers.
Policing Board member Dolores Kelly said she will be raising these questions with senior officers at the next meeting later this week.
"I think the district commander and others need to be across the detail of what's going on in their district," she said.
"There's an obligation for them to put bids in for what resources they need."
The SDLP assembly member said - given it had been clear after Ranger's victory on Saturday there was a strong possibility their first victory in a decade would be confirmed on Sunday - preparations should have been in place to prevent any large crowd gathering.
"There is a gold command structure around this to deal with these situations."
The PSNI had used its social media pages to "encourage anyone intending to celebrate today's Scottish Premier League result, to do so at home safely and within the current Health Regulations".
Ms Kelly said, while the service carries out risk assessments before any officer engagement with large crowds with a focus on `evidence-gathering' for future prosecutions, Board members "will want to see what the police operation was beyond what was on social media".
She said there is an argument for the service to be given enhanced powers of enforcement in line with those of the Gardai.
Sinn Féin MP Paul Maskey said the scenes were "deeply concerning in the midst of a pandemic", as were "reports of sectarian chanting".
"I will be raising questions directly with the PSNI around their approach to these organised gatherings.
"We have made great strides in our fight back against the pandemic thanks to the efforts of so many and we cannot allow that to the jeopardised.
"I would remind everyone of the ongoing need to follow the public health advice."
Speaking at the Assembly yesterday, First minister Arlene Foster was also critical of the Shankill gathering while congratulating Rangers on their title win.
"We have to abide by the public health regulation ... they are there to protect the community," the DUP leader said.
Loyalist Gary Lenaghan, who was pictured hugging east Belfast community worker Jim Wilson during the celebrations, told Radio Ulster's Stephen Nolan Show "it's football fans, it's emotion".
Both men insisted it had been a "spontaneous" gathering of young people in the area.
"Will I damn them and condemn them? No. Was it right? No," Mr Lenaghan said.
DUP assembly member Gregory Campbell urged people to wait and celebrate after "the vaccine has been rolled out".
"I understand the desire for celebrations but that doesn't justify breaking the public health rules."
He said it would be a bad day for Rangers supporters if the title celebrations ended with people in intensive care beds.
A super-spreader event is where a gathering of people leads to an outbreak of infections, which may have arisen from a single infected attendee.
Preventing such infection spikes is the main reason for the Executive's `Stay at Home' message and restrictions on gatherings both in and outdoors.
