The number of minors arrested with connection to organized crime has spiked in recent years, which is a shock to no one. According to a recent report from Reforma, 1,107 minors have been arrested for connections to organized crime under Calderón, with 339 of them being later accused. (This seems to indicate that almost 70 percent are released without trial. This is likewise not a shocker, given this report, but nonetheless a rather damning statistic.) The number of detainees was just 71 in 2007, but had jumped to 402 in 2010.
Calderón's government recently said that 30,000 people had been arrested for nacro-related crimes during his term. That would indicate that just 4 percent or so involved in the drug trade are minors. That seemed a bit low to me, but it is inline with the proportion of minors among those killed in drug-related crimes.