According to figures compiled by the Associated Press, between December 2006 and September 2009, security officers in Mexico arrested 226,667 suspects for drug crimes. Out of that total, less than a total have been officially charged with a crime.
The examples provided by the AP shows that 24,000 people were freed from Baja California out of the 33,000 that were arrested. In Sinaloa, 9,700 were arrested and 5,606 were released. And in the birthplace of the Gulf Cartel, 3,600 were arrested with 2,083 later released.
Source: Associated Press, “AP Impact: Mexico justice means catch and release,” Washington Post, July 27, 2010.