Crowds wait outside after police evacuated the Arndale Center in Manchester, England, on May 23. Police said an arrest made there was not related to the attack the day before at Manchester Arena. (Christopher Furlong/Getty Images)

With its red brick buildings, large villas and green lawns, the Fallowfield area of southern Manchester might appear to be an unlikely location for an investigation into Britain’s worst terrorist attack since 2005.

But on Tuesday, police forces launched at least three operations in Fallowfield and surrounding neighborhoods in connection with the devastating attack four miles away in the north of Manchester. Authorities identified the suspected suicide attacker as Salman Abedi, a 22-year-old British citizen of Libyan descent, and Fallowfield residents said he spent time in the area with his family.

In other communities at the center of recent terrorism investigations — such as the Molenbeek district of Brussels and some Parisian suburbs — authorities have openly acknowledged problems with Islamist extremism. Poverty, crime and high unemployment in these areas have long played into the hands of radicals, they say.

Manchester is different. Suburbs such as Fallowfield are mostly culturally or ethnically diverse and wealthy, with little to suggest that neighborhoods there have dealt with extremism for years.

But even before Monday’s attack, counterterrorism operations had focused on the small part of the city’s south.

Mourners attend a vigil for the people who lost their lives during the terror attack in Manchester, England. (Andy Rain/EPA)

Experts say Manchester’s hidden radicalization problem is not unique to the city.

“What we have seen recently is the emergence of clusters where groups of people — who often live close to one another — radicalize relatively quickly,” said Raffaello Pantucci, the director for international security studies at the Royal United Services Institute in London. “This isn’t only happening in London or Manchester, but also in much smaller towns.”

The British government has taken action as networks of extremists have developed across the country. Over the past few years, several laws have been passed to give authorities greater powers to arrest and prosecute attack suspects. Security services say they foiled 13 major terrorism plots between 2013 and March of this year. But at times, the expansive operations have come at a high price.

In 2010, authorities in the city of Birmingham set up surveillance cameras to monitor Muslims suspected of terrorism. But critics argued at the time that the operation placed all Muslims under suspicion. By the time the project was eventually stopped, it had damaged relations between counterterrorism officers and the city’s Muslim community. News of the surveillance scheme fed suspicion of authorities nationwide, officials say.

Manchester “has avoided making such mistakes,” said Jim Bonworth, a retired chief inspector with the Greater Manchester Police. “The British police very much relies on tips by community members. We cannot afford to lose their trust.”

Manchester’s experience shows that even praised community policing efforts struggle to prevent the radicalization of closed social circles across Britain.

“In the past, such radicalization processes have often taken place in mosques,” Pantucci said.

More recently, however, authorities have largely lost the ability to monitor terrorism suspects during their visits to mosques or community centers. Instead, groups of friends or acquaintances are meeting in apartments, making it nearly impossible for Britain’s stretched security services to monitor suspects, a dynamic that could explain the seemingly sudden emergence of groups of radicalized individuals in places such as southern Manchester.

Members of the community said they were distraught by the police operations in their districts Tuesday after the attack, which was claimed by the Islamic State.

“I sometimes saw him walk into his building alone or with friends,” said 32-year old Neville Edwards, a neighbor of the suspect. “But nobody here ever really talked to him.”

In Manchester’s Libyan community, Abedi was not unknown, however.

A man who identified himself as a friend of the Abedi family said many of the Libyans who live in the area fled the government of Moammar Gaddafi and supported the uprising against his regime.

“The Libyan community was standing by the rebels,” he said, speaking on the condition of anonymity for security reasons.

“I saw the boy here and there and we were even once on the same flight to Libya, but we weren’t close,” he said of the suspect. “I am more from his father’s generation.”

“We don’t know what happened to him or why he committed this attack on behalf of Daesh,” he said, using the Arabic acronym for the Islamic State. “But we are worried that this might make us Libyans look very bad.”

A taxi driver from the area said he had never seen Abedi but had witnessed the aftermath of attack. The man said he was parked outside the venue where the concert was taking place Monday night when he heard the explosion. He then picked up two survivors.

“This is such a cosmopolitan city, but there are circles and groups of people which are extremely closed to outsiders,” said the man, who spoke on the condition that only his first name, Jay, be used. “That is where teenagers or young men and women become radicalized. If it can happen here, it can happen anywhere.”

Pointing at a school in front of him, he added, “That’s the school two twin girls attended until they traveled to Syria to join the Islamic State.” Their case made international headlines.

Three years later, TV satellite trucks are on the same street again.

Abedi lived in the same neighborhood as the school, according to his former neighbors.