Colombian officials say a car bomb has killed at least four people in the Pacific port of Buenaventura. They also report an undetermined number of wounded.Chief provincial prosecutor Jose de la Pava tells The Associated Press that the bomb exploded in the city's administrative center near the mayor's and prosecutor's offices.Buenaventura is Colombia's main Pacific port and it is a politically volatile city that is rife with rival criminal bands and drug trafficking.There was no immediate claim of responsibility for the bombing.Outgoing President Alvaro Uribe has put leftist rebels on the defensive but they remain capable of damaging attacks.