London (CNN) -- Years before two men allegedly hacked a British soldier to death on a London street, Kenyan authorities arrested one of the suspects on suspicion of terror ties.
In 2010, Kenyan police detained Michael Adebolajo and six others suspected of links to Somalia's Al-Shabaab terrorist group, Kenyan government spokesman Muthui Kariuki said.
Kenyan counterterrorism sources told CNN that Adebolajo traveled to Kenya in November 2010 and was arrested for trying to cross illegally into Somalia.
Authorities have offered different accounts of what happened next.
The Kenyan government spokesman told CNN that British security officials interrogated Adebolajo, a 28-year-old British national of Nigerian descent who went by a different name at the time.
The British Foreign Office said that it provided consular assistance to a British national arrested in Kenya in 2010, but declined to provide further details.
It's unclear why Adebolajo traveled to Kenya or what happened after his 2010 arrest.
But authorities are looking into his travels to the region as part of their investigation into the soldier's killing Wednesday in Woolwich, a working class neighborhood in southeast London.
CNN understands that one line of inquiry being examined in the Woolwich terror investigation is that Adebolajo might have attempted -- but failed -- to travel to Somalia on another occasion, as recently as last year.
Last week's attack near the Royal Artillery Barracks shocked people across the United Kingdom, sparked a series of arrests over the weekend and prompted officials to announce plans for a task force to tackle extremism in Britain. On Saturday, angry far-right protesters in northern England pointed to the soldier's slaying and called for Muslims to leave the United Kingdom.
At the scene of the gory attack, one of the suspects apparently approached a man filming the scene in the Woolwich neighborhood and suggested that Rigby had been targeted "because Muslims are dying daily" at the hands of British troops like him. "We must fight them as they fight us," he said in the video aired by CNN affiliate ITN. "An eye for an eye and a tooth for a tooth."
Friends, acquaintances and British media have identified Adebolajo as the suspect seen in the gory video.
Authorities have not identified that individual or the 22-year-old man seized with him at the scene by armed police. Both suspects were shot and remain hospitalized.
British authorities, including Prime Minister David Cameron, have described the soldier's brutal slaying as a terror attack.
In total, six people have been arrested in connection with the attack, including three men who were taken into custody Saturday, and another on Sunday.
The men were being held on suspicion of conspiracy to commit murder, the Metropolitan Police said in a statement.
'Changed and withdrawn'
Adebolajo was a changed man when he returned to the United Kingdom from Kenya, according to a man who described himself as an associate of the suspect.
In an interview with BBC's "Newsnight," Abu Nusaybah said Adebolajo was physically assaulted and sexually threatened during his detention in Kenya -- an allegation CNN has not independently verified.
Adebolajo appeared changed and withdrawn after his return from the east African nation, Abu Nusaybah said.
Afterward, Abu Nusaybah said, Britain's MI5 domestic intelligence service approached Adebolajo and asked if he wanted to work for them.
A security source told CNN that "we would never comment" on the kind of allegations Abu Nusaybah made in the interview.
After the interview, British counterterrorism police arrested Abu Nusaybah, accvording to a BBC staffer who did not wish to be named.
London's Metropolitan Police Service said a 31-year-old man had been arrested in London on Friday night on terrorism-related offenses, but following standard practice, would not give the arrested man's name.
A Scotland Yard spokesman told CNN the arrest at the BBC was not connected to the murder investigation in Woolwich.
Islamist connections claimed
Adebolajo had been a follower of Al-Muhajiroun, a British group of Islamic extremists virulently opposed to UK intervention in Iraq and openly supportive of al Qaeda, according to several Al-Muhajiroun insiders.
He attended meetings of the group in London, they said, before moving away from the group two or three years ago.
Details about his purported connections to Somalia's Al-Shabaab movement are unclear.
The Islamist militants control much of southern Somalia and have long been affiliated with al Qaeda.
In 2011, Kenya sent forces to the neighboring nation to battle Al-Shabaab, which it blamed for kidnapping foreigners and launching grenade and gun attacks in Kenya.
Kariuki, the Kenyan government spokesman, said that Adebolajo was arrested in the coastal town of Lamu in 2010 and released to British security officials inside Kenya. No charges were filed against Adebolajo, according to the Kenyan media.
Lamu is part of an area near the Somali border that has been the stage for attacks by armed gangs and suspected operatives from Al-Shabaab.
On Sunday, one Kenyan official pointed to the 2010 arrest of Adebolajo and other British nationals as a sign that his country's approach fighting terrorism was working.
"On (the) war against terrorism, Kenya security forces have been ahead of the curve," said Bitange Ndemo, who heads Kenya's information ministry. "In 2010 our security forces arrested a number of British nationals on suspicion of terrorism activities. Relevant British authorities in Kenya were contacted. This action reaffirms Kenya's position as a credible and highly effective player in the fight against terror and organized crime."
CNN's Zain Verjee and Bharati Naik reported from London. CNN's Catherine E. Shoichet wrote the story in Atlanta. CNN's Erin McLaughlin and Laura Smith-Spark contributed to this report.