"He doesn't have any connection to him," Hoffman said. "He's never spoken to him, doesn't know him."
Hoffman said Khan, 27, came to the United States from his native Pakistan about eight months ago. He described Khan as a "scared young man" who doesn't understand why he was arrested last week.
Khan, his roommate, Pir Khan, 43, and a third man, Mohamad Rahman, of South Portland, Maine, are being held on immigration charges after their arrests Thursday.
Authorities say the men funneled money to Shahzad but may not have known how the money would be used.
A law enforcement official speaking to The Associated Press on condition of anonymity regarding the ongoing investigation said Shahzad may have tapped into an informal network of brokers called a hawala to transfer money and fund the failed plot to detonate a bomb inside an SUV parked near a string of busy restaurants and a Broadway theater showing "The Lion King" on May 1.
Smoke spewed from the SUV, but the bomb didn't go off. Police evacuated the area while dismantling the bomb, and no one was injured.
Shahzad, a budget analyst who lived in Connecticut, was arrested two days later at New York's John F. Kennedy International Airport while aboard a plane destined for Dubai.
Shahzad, 30, has waived his right to appear in court since his arrest on charges he tried to blow up an SUV packed with gasoline and propane and continues to provide investigators with information, prosecutors say.
Kifyat Ali, a cousin of Shahzad's father, has called Shahzad's detention "a conspiracy so the (Americans) can bomb more Pashtuns," a reference to a major ethnic group in Peshawar and the nearby tribal areas of Pakistan and southwest Afghanistan.
Hoffman described his time with Khan as a routine visit his office would make to any Pakistani citizen arrested in the United States. He said Khan, who was accused of overstaying his visa, asked him to arrange for an imam to visit him in jail and to tell his friends he is being held at the Suffolk County House of Correction in Boston.
Khan does not have an attorney, Hoffman said.
"He's a troubled fellow speaking very little English and wondering what's happening," Hoffman said.
Hoffman said he plans to visit Pir Khan, who is being held at the Plymouth County House of Correction, on Tuesday and will visit Rahman in Maine later this week.
Rahman, a computer programmer, acknowledged he once knew Shahzad, but he said he hadn't seen him for eight or nine years, according to Larry Adlerstein, his boss at Artist and Craftsman Supply in Portland.
Adlerstein said that after the attempted car bombing, he asked Rahman what it felt like to be from Pakistan, given the concerns over terrorism.
"He said, 'I feel terrible. As a matter of fact, I know this guy from the New York ... bomb incident,"' Adlerstein said.
Naseer Khan, who lives in Cambridge and is a former roommate of Pir Khan, said Pir Khan came to the United States about 20 years ago and often worked two jobs to send money back to his wife and teenage son in Pakistan. He said Pir Khan never expressed radical views or hatred toward America.
"He's a very, very good person and a very hardworking person," he said.