Amnesty International has urged the Mexican government to thoroughly investigate links between drug and criminal gangs and public officials, following the arrest this week of 16 police officers accused of working with gang members responsible for mass killings near the US border.More than 120 bodies have been found in the last 10 days alone in mass graves in Tamaulipas state, on a route used by migrants travelling to the USA.Amnesty International has repeatedly documented collusion between criminal gangs and public officials in abuses committed against migrants and others, but officials are rarely prosecuted for human rights violations. “The arrest of 34 suspects is a positive step, but with 16 police amongst those implicated it shows how criminal gangs and their accomplices in the security forces often operate with impunity to commit grave abuses,” said Rupert Knox, Researcher on Mexico at Amnesty International.”In the case of Tamaulipas, the heavy presence of federal police and army in the region did not prevent these killings or the collusion with criminal gangs.””It is crucial that a full, impartial and prompt investigation, which ensures respect for human rights, continues to identify all those responsible in order that they are brought to justice and the public are provided with reliable information on the actions taken. “In turn the discovery of mass graves has served to highlight the Mexican government’s wider failure to deal with the country’s public security crisis and to reduce criminal violence which has left many populations vulnerable to attacks, abductions and killings.”“It is vital that there are wider investigations to expose the collusion between security forces and criminal gangs in other areas of the country and prevent such grave abuses occurring again.” The mass graves were found last week in San Fernando municipality in Tamaulipas state, in the north of the country, where drug trafficking and other criminal gangs operate. The 16 officers arrested are all local municipal police.Information on the identity of victims remains scarce, but it seems likely that they were not connected with drug gangs. Tamaulipas is also part of the route travelled by Mexican and non-Mexican migrants on their way to the USA. At least some of the victims are believed to have been forced from long-haul buses at gunpoint at the end of March.Amnesty International has called for the rapid and reliable identification of the victims and the respectful treatment of the hundreds of relatives seeking to verify if their loved ones are amongst the victims.There have been reports of abductions of migrants travelling through Tamaulipas toward the northern border for many months, but little action was taken to investigate.In August 2010, the bodies of 72 irregular migrants were found in the same municipality of San Fernando. Several reported gang members have been arrested in connection with this killing but the identity of 16 victims remain unknown.”Only now on this new discovery of bodies is any action being taken. This is an indication of the limited impact of public security policy to ensure the safety of the population.” said Rupert Knox.The government has acknowledged there were more than 15,000 gang related killings in 2010 and more than 34,000 since President Calderón took office at the end of 2006 The vast majority have never been adequately clarified.There are also hundreds of cases of abductions that remain unsolved and the whereabouts of the victims unknown.