Arrests part of a string of high-level apprehensions targeting Michoacan drug cartel . Federal policemen stand at a checkpoint in the state of Michoacan last week . CNN suspected in slayings of Six federal police officers Tuesday . Man accused of being group 's bookkeeper arrested this month , authorities say .
Arrests part of a string of high-level apprehensions targeting Michoacan drug cartel . CNN suspected in slayings of Six federal police officers Tuesday . Man accused of being group 's bookkeeper arrested this month , authorities say .