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 .
Arrests part of a string of high-level apprehensions targeting Mexican drug cartel . La Familia Michoacana suspected in slayings of 12 federal police officers this month . Man accused of being group 's bookkeeper arrested Tuesday , authorities say .