The man British police say blew himself up as a packed concert was letting out in Manchester, England, Monday night is believed to have traveled to Syria and had "proven" links with the Islamic State terror network.

British and French intelligence have information that Salman Abedi, 22, had been to Syria, although it was unclear if he was part of a larger network of attackers, French Interior Minister Gerard Collomb said Wednesday.

Collomb spoke with British Prime Minister Theresa May and said the two countries should continue cooperating closely on counterterrorism efforts despite Britain's pending exit from the European Union.

It also was reported the attacker had recently returned to the U.K. from Libya days before the attack, according to his friends.

Abedi — who was born in Britain to Libyan parents — had traveled to the war-torn North African nation "three weeks ago and came back, like, days ago," a friend told The Times of London.

Now, investigators are attempting to learn whether the university dropout attended a terrorist training camp in Libya, where ISIS and Al Qaeda fighters are engaged in a bloody war against government forces.

NEW ARRESTS IN MANCHESTER INVESTIGATION

Meanwhile, The Sun reported that investigators also were looking at the possibility that Abedi had traveled to Syria from Libya without drawing the notice of British authorities. "His potential ties to Syria now very much forms one line of inquiry," one source told The Sun late Tuesday.

However, security sources told The Times their top priority was determining who built the bomb that caused such carnage at the Manchester Arena Monday night. Detectives who have viewed closed-circuit TV footage tell the paper that Abedi placed an explosive-laden suitcase on the ground in the foyer of Manchester Arena at around 10:30 p.m., as a concert by pop star Ariana Grande was ending.

Moments later, the bomb exploded, killing at least 22 people and injuring nearly 120 others. It was the deadliest terror attack on U.K. soil since a quartet of suicide bombers killed 52 people in central London in July 2005.

MANCHESTER VICTIMS IDENTIFIED

As Great Britain's terror threat was raised to its highest level for the first time in a decade, counterterrorism officers feared that the person who constructed the "sophisticated" explosive device could be on the loose.

Earlier Tuesday, at least 20 heavily armed, helmeted police surrounded a house listed as Abedi's address in the Fallowfield area of south Manchester and blasted down the door.

The British electoral roll lists Salman Abedi and Ismail Abedi as current residents of the house. Others with the same name are recorded as living there in previous years. Ismail Abedi, 23, was arrested on a nearby street and remained in custody Tuesday evening.

Neighbors remembered the suspected suicide bomber as a tall, thin young man who often wore traditional Islamic dress.

Alan Kinsey, 52, who lives across the street, told the Associated Press he had seen "a lot of different people living there" in the past but in the last six months or more had only seen one young man in his 20s. Kinsey said he would often get picked up by another young man in a Toyota and often returned late.

"I thought he worked in a takeaway or something" because of his late hours, Kinsey said.

Other neighbors said Abedi had grown a beard in the past year, would chant Islamic prayers loudly in the street and flew the green flag of Libyan Islamists from the roof of his house.

A male relative of Abedi's told the Sun that he had seen him approximately ten days before the attack looking "happy, relaxed and smiling."

The family member added that Abedi's parents had recently returned to Libya, having initially fled to Britain to escape the rule of late dictator Muammar Qaddafi. He added that the suspected terrorist had been a keen soccer fan, supporting European club giants Manchester United and Real Madrid.

"We can't believe it. We can't take it in. It is terrible," the family member said of the attack. "It shows that it takes a short amount of time [to] change someone, sometimes."

The Associated Press contributed to this report.