FBI wait to quiz Dzhokhar Tsarnaev amid relief over suspect's capture People draped flags along Boylston Street, near to where the two bombs were detonated. Photograph: Michael Reynolds/EPA Special agents trained with interrogating high-value suspects were waiting Saturday to question Dzhokhar Tsarnaev, the 19-year-old alleged Boston marathon bomber who remains in a serious medical condition at one of the city's hospitals. The suspect was brought late on Friday night to Beth Israel Deaconess medical center - the same hospital where earlier in the day his brother Tamerlan died having been shot in a massive gunfire with police. The capture of the younger brother led to an outpouring of celebrations across Boston, with people draping trees with the American flag along Boylston Street, near to where the two bombs were detonated. In Dorchester, where one of the victims, eight-year-old Martin Richard, lived, people set off fireworks. With a week-long manhunt for the suspects now over, and Boston getting back to normal following a virtual lockdown of the city on Friday, thoughts are now turning to the unanswered questions raised by the marathon bombings. The younger Tsarnaev was not read his Miranda rights - including his right to remain silent - at his arrest under a public safety exception, allowing investigators to grill him about possible accomplices or networks that might have conspired in the attacks. It was a decision supported by some, including Republican senators Lindsay Graham and John McCain, who called for Tsarnaev to be classified as an "enemy combatant." But civil rights advocates gave warning over the move. The American Civil Liberties Union said the public safety exemptions from Miranda rights should not be "open-ended" and that America "must not waiver from our tried and true justice system." US prosecutors are considering how best to press charges against Tsarnaev, bearing in mind his medical condition. They might wait for him to recover sufficiently to be taken to the federal courthouse in South Boston, or they might even request a federal judge comes to the hospital to charge him at the bedside. In the meantime, armed guards stood by his bedside at a hospital where many of the wounded from Monday's bombing were taken. US officials said a special interrogation unit specialised in dealing with high-value suspects were waiting to question the 19-year-old. Once federal investigators are allowed access to Tsarnaev, they will be keen to quiz him on his connections - in the US, in Dagestan, where his father lives, and Chechnya, where Tamerlan Tsarnaev is thought to have visited last year. Overnight, the FBI took two men and a woman in New Bedford, Massachusetts, in to custody and are questioning them about their links to Dzhokhar Tsarnaev. Much of the investigation is likely to focus on the activities of Dzokhar's elder brother. The FBI has revealed that in 2011 Tamerlan was interviewed by its agents at the request of an unnamed foreign government - widely reported to have been Russia - who asked the bureau to look into whether Tamerlan, then 24, had extremist connections. In a statement, the FBI said that the foreign government had information that Tamerlan Tsarnaev was a "follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States for travel to the country's region to join unspecified underground groups." In response to the request, the FBI scoured Tamerlan's telephone records, online history, associations with other people, movements and educational history, and agents interviewed him and his relatives. But the bureau found no evidence of terrorism activity either at home or abroad. It passed on its findings to the foreign government. The FBI is now likely to retrace its steps and repeat that search more thoroughly. Tamerlan Tsarnaev's six-month visit to Russia last year will be of particular interest to federal agents. During the visit he stayed with his father, Anzor Tsarnaev, in Makhachkala, Dagestan, and visited the family's ethnic home of Chechnya, it is believed. Speaking from Russia, Zubeidat Tsarnaeva, the suspects' mother, suggested that Tamerlan had already been subjected to FBI surveillance. "They knew what my son was doing, they knew what sites on the internet he was going to," she told state television.