By Eve Brennan, Lauren Said-Moorhouse and Helen Regan, CNN

London (CNN) — Dozens of people, including four children, were injured when a driver plowed a car into aparade in northwest England celebrating Liverpool Football Club’s latest Premier League win on Monday evening.

A 53-year-old white British man from the Liverpool area, believed to be the driver, was arrested at the scene, according to Merseyside Police. Describing the collision as an “isolated incident,” police said they were not looking for any other suspects and were not treating the incident as terrorism.

Police will reveal the findings of an investigation into the collision so that “all the facts are known,” according to Liverpool’s mayor, Steve Rotheram.

“It’s not for people on social media to be speculating what happened,” the mayor told CNN on Tuesday, describing the “terrible event” late Monday. “The police are the only people who have all of that information to hand – and they are the people we should trust.”

Footage from Reuters news agency on Tuesday morning shows the scene littered with debris and closed off with police tape. A police van is parked across the street, blocking the road.

Hundreds of thousands of jubilant soccer fans had lined the streets in the heart of Liverpool on Monday, waving flags and flares of red smoke, to watch an open-top bus victory parade to celebrate the iconic club’s 20th top-flight league title.

As the parade was winding down, those scenes of joy turned to chaos. Video from social media appears to show a gray minivan plowing into red-clad supporters. The angry crowd can then be seen surrounding and rocking the stopped vehicle.

A total of 27 people were taken to hospital, the head of service at North West Ambulance Service NHS Trust David Kitchin told a news conference. Four of those were “very ill in hospital,” according to Rotheram.

Four people – three adults and one child – had to be removed because they were trapped underneath the vehicle, according to Chief Fire Officer of Merseyside Fire and Rescue Service Nick Searle. A further 20 people were treated at the scene for minor injuries, he added.

“This gray people carrier just pulled up from the right and just rammed into all the people at the side of us … It was extremely fast. Initially, we just heard the pop, pop, pop of people just being knocked off the bonnet of a car,” one fan, Harry Rashid, told the UK’s PA Media news agency.

Rashid, who attended the parade with his wife and two young daughters, said crowds of people ran over and started to smash the car’s windows. “It was horrible. And you could hear the bumps as he was going over the people … I saw people lying on the ground, people unconscious. It was horrendous. So horrendous,” he said.

Video posted on social media appears to show a confrontation between the driver and the crowd at one point during the incident. The car is seen stopped and some in the crowd can be seen kicking and punching the car, which then quickly reverses before driving off.

Onlooker Matthew O’Carroll told Britain’s PA news agency that he saw the car approaching the top of Water Street. He said the vehicle drove past a parked police van at a “decent” speed and that the driver was beeping as he went through the crowd.

Footage shared by Reuters news agency showed emergency services tending to people, some being carried into ambulances on stretchers. Photos from the scene also showed authorities cordoning off the heavily littered roads. Police set up a tent where the crash occurred.

“We heard a frantic beeping ahead, a car flew past me and my mate, people were chasing it and trying to stop him, windows smashed at the back,” Peter Jones, who had traveled to Liverpool to attend the parade, told the Associated Press. “He then drove into people, police and medics ran past us, and people were being treated on the side of the road.”

The local police force said they were contacted just after 6 p.m. local time (1 p.m. ET) “following reports a car had been in collision with a number of pedestrians” in the city center.

Merseyside Police said it had been working with the organizers of the parade and a “robust traffic management” plan was put in place before the incident unfolded.

“Extensive enquiries are ongoing to establish the circumstances leading up to the collision and it is vital that people do not speculate or spread misinformation on social media,” Merseyside Police’s Assistant Chief Constable Jenny Sims said in a statement.

‘You’ll never walk alone’

The parade on Monday – which coincided with a separate May public holiday in the UK – involved players from the Liverpool squad being driven around the city center in an open-top bus and gleeful fans had joined the festivities along the 10-mile (16 kilometers) route.

Figures from across the sporting world paid tribute to those who were injured by the attack, which survivors say left the city reeling after the celebrations.

Former Liverpool manager Jurgen Klopp, who attended the parade, said he was “shocked and devastated.” “Our thoughts and prayers are with all those who are injured and affected,” he posted on Instagram. “You’ll never walk alone,” he added, in reference to the club’s anthem. A titan of world soccer, the German notably led Liverpool to its first league title in 30 years, in 2020.

Longtime opponents Manchester United and, Everton Football Club, the local rival team to Liverpool FC, offered their condolences online – as did the Premier League.

UK Prime Minister Keir Starmer said the whole country “stands with Liverpool” on Tuesday. “My thoughts and the thoughts of the whole country are with all of those that are affected, those injured, which of course includes children, their families, their friends… Liverpool fans everywhere,” the prime minister added, thanking emergency services “who did a fantastic job and continue to do so.”

This story has been updated with the latest developments.