Police have been granted more time to question a boy over the deaths of three children in the Southport knife attack as officers arrested four men in connection with a night of violent disturbance.

The 17-year-old has been in custody since he was arrested in the Merseyside town on Monday.

Bebe King, six, Elsie Dot Stancombe, seven, and nine-year-old Alice Dasilva Aguiar died and eight other children were injured in the stabbings at a Taylor Swift-themed dance class.

A peaceful vigil took place on Tuesday evening but unrest broke out shortly afterwards near a mosque, leading Elsie’s mother to appeal for calm on social media.

Merseyside Police said the disturbance was believed to have involved English Defence League supporters and those behind the violence had been fired up by social media posts which suggested an Islamist link to the stabbings.

The 17-year-old boy, who was arrested on suspicion of murder and attempted murder after Monday’s attack, has no known links to Islam.

The suspect, who has not been named because of his age, was born in Cardiff and later moved to Banks in Lancashire, a village that lies a few miles north of Southport.

Five of the children remain in a critical condition, along with two adults, following the attack at the Hart Space centre in Hart Street.

The disturbance broke out outside Southport Mosque on St Luke’s Road, near the scene of the attack, a short time after thousands paid their respects to the dead and injured at a vigil at the Atkinson Theatre on Lord Street.

In a message widely shared on social media, Elsie’s mother Jenni Stancombe condemned the violence.

“This is the only thing that I will write, but please stop the violence in Southport tonight,” she wrote.

“The police have been nothing but heroic these last 24 hours and we don’t need this.”

A police representative said a 31-year-old from St Helens, a 39-year-old from Southport and a 31-year-old from West Derby in Liverpool had been held on suspicion of violent disorder, while a 32-year-old from Manchester, “with a probation address in Southport, was arrested on suspicion of affray and possessing a bladed article.

Chief Constable Serena Kennedy told a news conference though more arrested would likely follow.

“It’s impossible to say [how many will be arrested]. It’s really early days in the investigation,” she said.

“Initially, there were about 70 people who made their way away from the vigil and were making their way towards the mosque.

“They suddenly became about 200 in number and then others joined that number.”

She said 49 of her officers had been injured in the disturbance, along with four others from Lancashire Police who had been drafted in to help.

The force said eight “sustained serious injuries including fractures, lacerations, a suspected broken nose and concussion” and were treated in hospital.

They added that three police dogs were also suffered lacerations, cuts and burns.

Merseyside Police Federation’s Chris McGlade said his injured colleagues were the same “courageous officers” who were themselves trying to come to terms with the “unimaginable tragedy” of Monday’s attack.

A Section 60 Order giving police extra stop and search powers and the ability to disperse disruptive crowds remain in place.

Extra officers would also remain in the area for reassurance, police said.

The town’s MP Patrick Hurley said “thugs” travelled to the area to use the deaths “for their own political purposes”.

Home Secretary Yvette Cooper had earlier warned about disinformation linked to the attack.

Assistant Chief Constable Alex Goss said there had been “much speculation and hypothesis” around the teenager and “some individuals” were using it to “bring violence and disorder to our streets”.

“We have already said that the person arrested was born in the UK, and speculation helps nobody at this time,” he said.

Following the night of disorder, a clean-up operation began, with many members of the community coming together to help.

Volunteers brought brushes and shovels to clean up the Sussex Road and St Luke’s Road area following the riot.

Melted plastic from wheelie bins which were set alight could be seen stuck to the tarmac on St Luke’s Road.

Assistant Chief Constable Jenny Sims said there had been “a tremendous effort by members of the public” to help.

She said locals had assisted in cleaning up the streets, “using hose pipes and brushes, and donating food and dog food to officers to restore the pride and respect they have for their town”.

Ibrahim Hussein, chairman of Southport Mosque, said he was moved to see locals turn up to help rebuild parts of the mosque damaged in the disorder.

“It brings tears to my eyes because although I know the people of Southport and I know how beautiful they are, but this was still a moving experience to see all that,” he said.

A crowdfunding page which was launched by a Taylor Swift fans group in the aftermath of the attack to raise money for Alder Hey Children’s Hospital, which has treated many of those involved, has raised more than £300,000.

Additional reporting by Chris Long and PA Media.