May 24 (UPI) -- Greater Manchester Police Chief Constable Ian Hopkins said authorities are investigating a "network" of people who may have played a role in Monday's Manchester Arena bombing, which killed 22 people.
Hopkins' statement is the strongest yet by an official in confirming accused suicide bomber Salman Abedi did not act alone.
"We are carrying out extensive searches at premises across Manchester," Hopkins said at a press conference Wednesday."I think it's very clear that this is a network that we are investigating and it continues at pace and there's extensive investigations going on and activity taking place across Greater Manchester."
The Manchester Evening News reported police believe the man responsible for making the bomb used in the attack is still at large.
Twelve of the 22 fatalities have so far been identified as Saffie Roussos, 8; Martyn Hett, 29; Olivia Campbell, 15; Kelly Brewster, 32; John Atkinson, 28; Georgina Callander, 18; Jane Tweddle-Taylor, 51; Nell Jones, 14; Angelika Klis, 40; Marcin Klis, 42; Alison Howe, 45; and Lisa Lees, 47.
British Home Secretary Amber Rudd said Abedi "likely" had accomplices and she criticized the U.S. government for leaking information about his identity.
In addition to the fatalities, another 64 people were wounded, several of whom remain hospitalized with life-threatening injuries.
The Islamic State claimed responsibility, and Rudd suggested Abedi did not work alone. She did not reveal details of whom he may have worked with.
"It was more sophisticated than some of the attacks we've seen before, and it seems likely -- possible -- that he wasn't doing this on his own," Rudd said.
British police identified Abedi, a 22-year-old British citizen of Libyan descent, as the Manchester Arena bomber on Tuesday. Authorities were working to determine whether Abedi possibly received training from the Islamic State when he traveled to Libya to visit his parents, who had moved back to their home country.
French Interior Minister Gerard Collomb told BFMTV that Abedi had traveled to Syria as well as Libya and that he had "proven" links with the Islamic State.
Rudd also expressed frustration with the U.S. government, as news of Abedi's identity was first revealed in the United States. She said Britain wanted to control the flow of information to "keep the element of surprise" as security forces launched raids and made arrests in the wake of the attack, Britain's worst since 52 people were killed in the July 7, 2005, bombings targeting public transportation.
"The British police have been very clear they want to control the flow of information in order to protect operational integrity -- the element of surprise -- so it is irritating if it gets released from other sources, and I've been very clear with our friends that that should not happen again," Rudd said, adding she had been very clear with leaders in Washington, D.C., "that it should not happen again."
British police have so far arrested four men in total. Abedi's older brother was detained Tuesday and shortly before Wednesday's press conference three additional men were taken into custody. It was not clear why police had arrested any of the men.
In Libya, counterterrorism authorities said they arrested at least two members of Abedi's family, including a younger brother suspected of preparing an attack in Tripoli.
Many of those killed and injured in the Manchester attack include children and adolescents.
British Prime Minister Theresa May on Tuesday raised the terror alert from "severe" to "critical" -- the top level that indicates another terrorist attack could be imminent.
"It is a possibility we cannot ignore, that there is a wider group of individuals linked to this attack," May said.
The critical terror alert level permits British officials to deploy armed forces to secure potential target areas and to support police officers. May said soldiers would be placed in key public locations such as Buckingham Palace, Downing Street and the Palace of Westminster to support police.
May on Tuesday said a "single terrorist" -- prior to the revelation of Abedi's identity -- detonated an explosive device near an Manchester Arena exit at about 10:30 p.m. Monday, just after an Ariana Grande concert ended. She said the attacker chose the time and place "to cause maximum carnage and to kill and injure indiscriminately."
Britain's main political parties on Wednesday announced they would resume local and national campaigns for the June 8 general election on Thursday and Friday.