( CNN ) -- Police in Colombia have arrested four people accused of killing a U.S. Drug Enforcement Administration agent during an attempted robbery . Colombia 's National Police said the four suspects they arrested were part of a criminal network of thieves . Two additional suspects who were allegedly involved in the crime remain on the loose , CNN affiliate Caracol TV reported . The United States will request extradition of the suspects , but it has not yet done so formally , a law enforcement official said . U.S. officials have extradited and prosecuted suspects accused of killing U.S. federal agents in the past . Special Agent James `` Terry '' Watson , assigned to the DEA unit in Cartagena , was on temporary duty in Bogota when he died after being stabbed in a taxi cab last Thursday night , officials said . Authorities have said they do not believe the attack was connected to his work for the U.S. agency . `` The homicide of the DEA agent was committed by common criminals and was not connected to his work in Colombia , '' National Police Director Gen. Jose Roberto Leon Riano said , according to Caracol . U.S. officials praised Colombian authorities Tuesday for their swift investigation . `` The Drug Enforcement Administration is grateful for the outstanding work of the Colombian National Police , the Special Investigative Unit and the Attorney General 's Office that led to the swift arrest of these suspects , '' DEA Administrator Michele M. Leonhart said in a written statement . `` We will never forget Special Agent Watson and his sacrifice , as well as all those who have given their lives for the rule of law . We salute the brave and expeditious work of Colombian law enforcement and we look forward to justice being served . '' Watson , 42 , had been watching the last game of the NBA finals at a Bogota restaurant Thursday night and left in a taxi , a State Department spokesman said last week . Investigators believe Watson 's cab stopped at a traffic light and his assailants jumped out of two other cabs , which pulled up on either side of the vehicle in which he was riding , a law enforcement official said . According to the official , Watson managed to escape from the cab and was taken to a hospital , where he died . In Colombia , such attacks are known as `` millionaire rides . '' Authorities said the suspects they arrested were part of a gang known for millionaire ride robberies . The DEA said Watson was a 13-year veteran of the agency . He had been sent to Afghanistan three times on counternarcotics trafficking assignments and had previously served in the Army and worked for the U.S . Marshals Service . Attorney General Eric Holder is scheduled to speak at a funeral service for Watson in Louisiana on Wednesday .
Colombian police say they 've detained four suspects tied to DEA agent 's killing . Washington has submitted an extradition request for the suspects , police say . Two more suspects are at large , a CNN affiliate reports . The agent was killed in a robbery attempt ; officials do not believe it was tied to his work .