STOCKHOLM A team from the U.S. Federal Bureau of Investigation was helping Swedish police on Tuesday probe Saturday's bomb attack on Stockholm and looking for links to blasts in other countries.
The FBI presence underlines a growing conviction that Middle East-born suicide bomber Taymour Abdulwahab had accomplices.
Abdulwahab set off an explosion in his car, which burst into flames, and was killed when one of several devices he was carrying exploded prematurely, avoiding what police think was meant to be a far more lethal and destructive blast.
Abdulwahab's family moved to Sweden from the Middle East in 1992 but he apparently became more radical after moving to study and live in England.
"The investigation is going at full speed with witness interrogations and technical research," said Security Police spokeswoman Sofia Oliv.
The seven-strong FBI team is focusing on the fragments of bomb left on the street, and is trying to determine if there any links with blasts elsewhere, Oliv said. "They are specialists in searching fragments of explosive," she added.
Swedish investigators have said Abdulwahab probably had accomplices and that his likely targets were the busy central railway station or a large department store.
Security experts also think he may have had help planning or publicising the attack, pointing to information posted online about him, including messages from an admirer who threatened more such attacks unless Western troops left Afghanistan.
Thomas Hegghammer, an Islamism scholar at the Norwegian Defense Research Establishment, said the admirer could have some connection to the attack, but may have got Abdulwahab's name from pictures of the license plate of the bombed car, posted on non-militant websites on Saturday.
"There could be a couple of people in Sweden or in Luton who were directly involved, but I would be very surprised if Taimour took orders from ... AQ (al Qaeda) in Iraq," he added in a blog.
CLUES IN BRITAIN, SWEDEN
Investigators have been looking for clues in the southern England town of Luton where Abdulwahab lived with his wife and children, in the southern Swedish town of Tranas where he grew up, and in an apartment in the Stockholm suburb of Hasselby, where his wife's family are reported to live.
A neighbor in Hasselby said police had carried out a raid on the next-door apartment on Sunday morning.
"I was really scared -- I thought that someone was trying to break in," said Barlin, declining to give her full name. "My husband looked out and saw a lot of police running around."
Reuters could not confirm the apartment belonged to Abdulwahab's wife's family.
People at the Luton mosque which Abdulwahab attended in 2007 said he had initially been outgoing and friendly but had attracted attention after spreading radical views.
When confronted, he walked out and never returned.
Luton has a large Muslim community. The suicide bombers behind the July 2005 attack on London's transport system met there at the start of their operation.
(Editing by Tim Pearce)