UK Home Secretary Amber Rudd stated on Wednesday that Abedi had been on the radar of the British security services and had recently returned to the UK from Libya. US officials told CNN's Barbara Starr
that Abedi came back just days before the attack.
British intelligence services are now trying to answer a series of urgent questions, including whether Abedi had any contact with terrorist operatives while in Libya and whether he received any bomb-making training while he was there. A British counterterrorism official told CNN on Tuesday evening that British intelligence services had not yet uncovered evidence of such ties, but cautioned it was very early in the investigation.
Investigators will be careful not to jump to conclusions. After the 2013 Boston bombings, there was a great deal of speculation that one of the bombers, Tamerlan Tsarnaev, had received bomb-making instruction in Dagestan on a visit before the attack. No credible evidence has emerged that he met with any terrorist group while there and investigators concluded that he built his device by downloading instructions from the internet.
Abedi's travel is being scrutinized because recent intelligence obtained by the US
suggests that ISIS has set up an external operations wing in Libya tasked with plotting attacks in Europe. The group has already used Libyan soil to train recruits for attacks in Tunisia
Anis Amri, the Tunisian extremist who killed 14 in Berlin last December, was reportedly in communication with the group in Libya
before his attack via an encryption app.
As CNN was first to report
, after US intelligence detected the possible presence of terrorist operatives linked to Amri's attack in two camps near the Libyan coastal town of Sirte, the Obama administration on its last day in office dispatched two B-2 bombers to destroy the facilities.
In a news conference on January 19, outgoing Defense Secretary Ash Carter said: "Importantly, these strikes were directed against some of ISIL's external plotters, who were actively planning operations against our allies in Europe ... and may also have been connected with some attacks that have already occurred in Europe."
The presence of an ISIS external attack cell on the southern shores of the Mediterranean is especially concerning because thousands of irregular migrants
have been setting off from the Libyan coast and arriving by boat in Italy each month. In the autumn of 2015, several of the ISIS Paris and Brussels attack cell
posed as refugees to gain entry into Europe, during a huge influx of refugees through Turkey and Greece.
In the years since the fall of the Gaddafi regime, Libya has become a haven for terrorist groups, including ISIS. At the peak of the group's expansion in early 2016 it could draw on as many as 6,000 fighters
and controlled swaths of territory, including the town of Sirte
Although a Libyan government offensive had recaptured the town by the end of 2016, ISIS fighters are believed to have regrouped in areas to the southwest of Sirte -- including in the camps destroyed by the B-2 bombers, as well as in Libya's interior deserts.
One member of Manchester's sizeable Libyan community told CNN there had been concern that Abedi, like some other youngsters, had come under the influence of ISIS propaganda.
Last year Abdal Raouf Abdallah, 24, a British-Libyan resident of Manchester who was injured fighting against Gadhafi in the 2011 uprising was convicted of working to faciliate the travel of wannabe jihadis from the UK to Syria
Manchester is also the home of a sizeable contingent of former members of the Libyan Islamic Fighting group, a jihadi group that battled Gadhafi but never embraced Osama bin Laden's global jihad.
As CNN reported in 2012
, one former British-Libyan resident of Manchester, Abdulbasit Azuz, 51, was tasked by al Qaeda leader Ayman al Zawahiri with building the group's presence in eastern Libya after the fall of the Gadhafi regime.
Azuz's current whereabouts and status are unclear, but there were reports that he was detained inside Turkey in late 2014.
Jihadi groups aligned with al Qaeda are still believed to have a presence in eastern Libya, having helped push ISIS out of Derna and several other areas in 2015.
As well as investigating any interaction the attacker may have had with ISIS in Libya, US and UK intelligence services -- along with Africa Command -- are looking at the possibility Abedi could have met with operatives from al Qaeda in the Islamic Maghreb (AQIM), US officials told Barbara Starr.
AQIM, like ISIS, is estimated to still have hundreds of fighters inside Libya. The al Qaeda affiliate is believed by the US to be mainly based in south western Libya and trying to regain a higher profile after months of international attention being paid to ISIS, the officials said.
If it transpires that Abedi met with either group while in Libya, the high-profile battle to wipe out terror will have a pressing need to redirect its focus.