Mexico City ( CNN ) -- Authorities found two severed heads along a highway in Mexico City on Monday morning , the city 's attorney general said . The heads were inside a car near the border dividing the city from neighboring Mexico state , Attorney General Miguel Mancera told reporters . The nation 's defense ministry was also nearby . A lengthy message was left beside the heads , Mancera said , detailing that a drug gang known as `` The Hand With Eyes '' was responsible . `` It ends saying that the territory of 'The Hand With Eyes ' is so extensive that it has reached the metropolitan area and has n't disappeared , '' Mancera said . Police in Mexico City arrested the gang 's suspected leader , Oscar Osvaldo Garcia , also known as `` The Hand With Eyes , '' in August . Mancera said Monday that authorities remained committed to tracking down members of the gang and stopping its growth . Authorities were still working Monday to identify the victims . Beheadings have become a signature sign of the brutally violent turf battles between drug cartels that have plagued cities across Mexico . Last week authorities in the beach resort city of Acapulco made a similar discovery , finding five severed human heads inside a small wooden crate , Guerrero state authorities said . But such violence is rare in the country 's capital . `` Mexico City has been surprisingly calm in the midst of the turbulence of this conflict with organized crime , while other major cities are experiencing major upturns in violence , '' said Eric Olson , a security expert at the Mexico Institute of the Woodrow Wilson International Center for Scholars in Washington . `` It has n't exploded the way it has ( elsewhere ) . There 's always that fear of that happening , because there 's nothing to guarantee that it wo n't . '' CNN 's Krupskaia Alis , Rene Hernandez , Rafael Romo and Catherine E. Shoichet , and CNNMexico.com contributed to this report .
NEW : A message left by a drug gang claims responsibility , the city 's prosecutor says . NEW : Mexico 's defense ministry is near the site where the heads were found . The heads were found near the border between Mexico City and neighboring Mexico state . Brutal turf battles between drug cartels , common elsewhere in Mexico , are rare in the capital .