The Mexican army has confiscated guns from the entire police force of the town of Rosarito, near the Mexican border with the US.
Drug gangs are strong in Mexico's border region
Mexican authorities suspect that the town's police have been colluding with drug trafficking gangs.
Mexican troops carried out a similar crackdown in January on Tijuana police.
The Rosarito force's 200 guns will be examined to see whether any were used in an attack on the town's police chief earlier this month.
One of his bodyguards was killed in the attack.
'Purging the ranks'
"We recognise that the enemy is inside our house and for this reason we are purging the ranks - we need to have confidence in our police," Baja California state police chief Daniel de la Rosa said.
Drug gangs are strong in Mexico's border region, which includes Rosarito, a beach resort town south of Tijuana.
Mexican President Felipe Calderon has deployed about 25,000 troops to the region, and to the western state of Michoacan, since taking office 12 months ago.
Some 2,500 people have died so far in 2007 in turf wars between rival Mexican drugs gangs.