Six Mexico prison workers slain after crackdown.

By Hugh Dellios, Chicago Tribune Knight Ridder/Tribune Business News

Jan. 21--MEXICO CITY -- Six employees of a federal prison near the Texas border were shot to death and dumped outside the prison Thursday, apparently in retaliation for a weeklong crackdown on corruption involving jailed drug lords.

The slayings reportedly occurred near the maximum-security prison in Matamoros, where some of Mexico's most notorious narco-traffickers were transferred this week after a dramatic police raid last week backed by army tanks on the La Palma prison outside Mexico City.

Mexican officials vowed not to back down on their campaign to clean up La Palma and other prisons, where notorious drug capos were still running their trafficking operations and ordering the killing of rivals despite their incarcerations.

"In no way are we going to lower our guard. In no way will we slow down in the battle," said Interior Secretary Santiago Creel.

Atty. Gen. Rafael Macedo de la Concha said officials …