News that El Salvador police may have masterminded the 2009 murder of a top DEA informant is a sign of the formidable issues facing U.S. efforts to collaborate with local law enforcement.

Edwin Argueta Contreras, alias “El Porras,” was murdered in San Salvador in August 2009. He was an alleged drug smuggler and “coyote,” or human trafficker, turned informant for the U.S. Drug Enforcement Administration (DEA), and had helped build cases against many members of the Perrones, a powerful local trafficking group. He reportedly agreed to cooperate with the authorities after learning that a murder attempt against him in March of that year was the work of some of his closest trafficking allies.

Since then, Argueta had been a very valuble source of intelligence for the DEA, reportedly handing over information on Perrones allies including mayors and members of congress. He also gave key evidence against Daniel Quezada, a Perrones boss, who was arrested in April 2009.

After surviving his first assasination attempt — a gunshot wound to his back — Argueta was kidnapped in August, along with four friends, from a bar in San Salvador. He was tortured to death, and his body was found the next day in a vacant plot of land on the outskirts of the city.

At the time, the authorities said his murder was likely the product of a vendetta between gangs, and that the suspected killers had ties to a Guatemalan group linked to the Perrones. There were also suggestions, however, that the death might have been triggered by a leak within the police force, which revealed Argueta’s role as a double agent. Salvadoran newspaper La Prensa Grafica reported that the officer who served as Argueta’s liaison with the DEA was dismissed after the killing.

Nearly two years on, a report in the same paper said that, according to official sources, two police officers are currently suspected of leading the operation to kill Argueta. One of the suspects is reportedly a local officer from Soyapango, the area where Argueta’s body was found, while the other is a member of the anti-narcotics force (DAN). According to La Prensa Grafica’s sources, it is likely that either the officers were hired by the Perrones to kill him, or that the men were trying to stop Argueta from revealing their links with the group.

The Perrones are a native Salvadoran trafficking federation that runs drug operations in the east of the country. They have long been known to have deep ties with local institutions. A report by the Wilson Center details allegations that, in some parts of the country, the entire political system relies on the Perrones, and that various prominent public figures are allegedly entangled with the traffickers. The group has seemingly penetrated the national police (PNC) at various levels, including the anti-narcotics department. In 2008 one 10-year veteran of the drug force was caught in a car heading to Guatemala with thousands of dollars in cash, which he confessed was to be used to buy drugs. Authorities said that he was working with the Perrones, and for years had, together with another officer, tipped off the group about police operations. In 2010 a former head of the drug division, Godofredo Miranda, was investigated for alleged links to the Perrones.

Before becoming a DEA informant, Argueta reportedly boasted of his links with the police, claiming he had friends in the anti-narcotics division. The two officers suspected of his murder are thought to have led him to his death, having spent time with him earlier in the day and then invited him to the bar where he was seized by gunmen. This suggests that he trusted the officers, and that they may have been his long-time police contacts.

The current investigation into the two officers, if successful, could indicate that El Salvador is moving forwards with the police reforms that the president has promised. At a conference in June President Mauricio Funes announced that the country was in the midst of reforms, and said “it is necessary to carry out a permanent and deep process of purification” of law enforcement bodies. Funes said that 150 police had been removed from their posts under his government, due to their links with organized crime.

Cases like the death of Argueta highlight the difficulty of El Salvador’s fight against the drug trade, and the power that criminal organizations hold in the country. It undermines the U.S.’s work with El Salvador, which it has called a “key partner” in the region, casting further doubt on the ability of the local police to serve as a partner with the U.S. authorities.