Police warned Sunday that efforts to deal with the violence that has erupted across towns and cities in recent days in the wake of a stabbing rampage at a Taylor Swift-themed dance class that left three girls dead and several wounded means that other crimes may not be investigated fully.

The warning comes a day after dozens of people were arrested as anti-immigration activists faced off with migrant protesters across the U.K., with violent scenes played out in many locations across the country, from the Northern Ireland capital, Belfast, to Liverpool in the northwest of England and Bristol in the west. Further arrests are likely as police scour CCTV, social media and body-worn camera footage.

In just one incident on Saturday, Merseyside Police said about 300 people were involved in violent disorder in Liverpool, which saw a community facility being set on fire. The Spellow Lane Library Hub suffered severe damage to the ground floor. Police said rioters tried to prevent firefighters from accessing the fire, throwing a missile at the fire engine and breaking the rear window of the cab.

Liverpool City Region Mayor Steve Rotheram said the attack was not just on the building but “on our very community” and “an insult to those families still grieving and survivors still struggling to make sense of Monday’s attack.”

Further gatherings are scheduled Sunday and police will continue to mount a significant security operation, deploying thousands more officers onto the streets, many in riot gear. Police have also made more prison cells available and are using surveillance and facial recognition technology.

“We’re seeing officers that are being pulled from day-to-day policing,” a spokeswoman for the Police Federation of England and Wales, Tiffany Lynch, told the BBC. “But while that’s happening, the communities that are out there that are having incidents against them — victims of crime — unfortunately, their crimes are not being investigated.”

The violence erupted earlier this week in protest of Monday’s stabbing attack in Southport. The 17-year-old male son of immigrants from Rwanda has been arrested.

False rumors spread online that the young man was a Muslim and an immigrant, fueling anger among right-wing protesters. Suspects under 18 are usually not named in the U.K., but Judge Andrew Menary ordered Axel Rudakubana, born in Wales, to be identified, in part to stop the spread of misinformation.

Police said many of the actions are being organized online by shadowy nationalist groups, who are mobilizing support online with phrases like “enough is enough,” “save our kids” and “stop the boats.” Counter-protests are also anticipated with the organization Stand Up To Racism.

Calls for protests have come from a diffuse group of social media accounts, but a key player in amplifying them is Stephen Yaxley-Lennon, a longtime agitator who uses the name Tommy Robinson. He led the English Defense League, which Merseyside Police has linked to the violent protest in Southport on Tuesday, a day after the stabbing attack. The group first appeared around 2009, leading a series of protests against what it described as militant Islam that often devolved into violence.

The group’s membership and impact declined after a few years, and Yaxley-Lennon, 41, has faced myriad legal issues. He has been jailed for assault, contempt of court and mortgage fraud and currently faces an arrest warrant after leaving the U.K. last week before a scheduled hearing in contempt-of-court proceedings against him.

Brexit champion Nigel Farage, who was elected to parliament in July for the first time as leader of Reform U.K., has also been blamed by many for encouraging — indirectly — the anti-immigration sentiment that has been evident over the past few days. While condemning the violence, he has criticized the government for blaming it on “a few far right thugs” and saying “the far right is a reaction to fear … shared by tens of millions of people.”

Right-wing demonstrators have held several violent gatherings since the stabbing attack, clashing with police Tuesday outside a mosque in Southport — near the scene of the stabbing — and hurling beer cans, bottles and flares near the prime minister’s office in London the next day. Many in Southport have expressed their anger at the organized acts of violence in the wake of the tragedy.

The attack Monday on children at a Taylor Swift-themed summer dance class shocked a country where knife crime is a long-standing and vexing problem, though mass stabbings are rare.

Rudakubana has been charged with murder over the attack that killed Alice Dasilva Aguiar, 9, Elsie Dot Stancombe, 7, and Bebe King, 6. He has also been charged with 10 counts of attempted murder for the eight children and two adults who were wounded.

Britain’s new prime minister, Keir Starmer, has blamed the violence on “far-right hatred” and vowed to end the mayhem. He said police across the U.K. would be given more resources to stop “a breakdown in law and order on our streets.”