An American woman wanted for allegedly dragging a cyclist for two-and-a-half blocks in a fatal crash was living in Adelaide when the FBI tracked her down.

Andrea Dorothy Chan Reyes vanished after she was accused of vehicular manslaughter over the death of California father-of-three Agustin Rodriguez Jr in January last year.

But she is now in Australian custody awaiting extradition after she was arrested in the northern Adelaide suburb of Paralowie.

The arrest was made on April 17 by AFP officers after a provisional request by the FBI.

Andrea Dorothy Chan Reyes allegedly ran over Agustin Rodriguez Jr before fleeing the US to Australia. (Google Plus)

Chan Reyes allegedly struck Mr Rodriguez at speed about 7.30am on a Monday morning near Los Angeles last January.

FBI special agent Erik Arbuthnot wrote in court filings that Chan Reyes was speeding and drove into opposing lanes before the collision.

Mr Rodriguez was allegedly dragged more than 200m by Chan Reyes' Lexus before his body was left in the roadway.

"He was definitely a family man, he was a gentle, kind person, there isn’t a person who could say a bad thing about him," his niece Angelica Miller told CBS Los Angeles after his death.

Chan Reyes allegedly fled from the US to Hong Kong five days after the collision, but was identified in court documents the following month as the suspect.

After the crash Chan Reyes allegedly took the Lexus to a body shop in nearby Huntington Beach to replace the windscreen, telling workers there she had hit a deer.

The Los Angeles County Sheriff's forensic lab was able to match DNA from the Lexus to Mr Rodriguez, the FBI report states.

A warrant was issued for Chan Reyes' arrest in September, but it was eight months before she was tracked down to Adelaide and arrested.

News of Chan Reyes' arrest was met with an outpouring of relief from Mr Rodriguez's family and friends.

"Wheels of justice sometimes turns slow, but I hope she finally pays for her crime," JC Granados wrote today on a Facebook page named Justice for Agustin Rodriguez Jr.

"I'm so happy they found her," Susie Diaz wrote.