JUAN MANUEL SANTOS chose his words carefully after signing a peace deal with Colombia’s FARC guerrillas in 2016, officially ending a 50-year-long conflict. “Today marks the beginning of the end of the suffering, the pain and the tragedy of the war,” the president said, well aware that reintegrating the FARC into society would bring its own travails. Overall, the peace process has succeeded; the Colombian countryside is safer than it has been in generations. But a few holdouts still trouble Mr Santos, whose presidency ends on August 7th, and will test his successor as well.

On April 13th Lenín Moreno, the president of Ecuador, announced that two of his country’s journalists and a driver had been killed near the Colombian border. They had been kidnapped on March 26th by the Oliver Sinisterra Front, a gang of 70-80 former FARC guerrillas who refused to demobilise and broke off from the organisation. Led by an Ecuadorean named Walter “Guacho” Artízala, the splinter group has sought to retain a piece of the lucrative trade making cocaine in southern Colombia and northern Ecuador and shipping it via the Pacific Ocean. Its fighters often attack Ecuadorean security forces.

Mr Moreno promised last month to send 12,000 soldiers and police to the region to fight drug gangs, and in response to the abductions the two countries have arrested 43 alleged members of the front. But determined guerrillas in mountainous terrain can prove remarkably resilient. On April 17th the Ecuadorean government announced that the Oliver Sinisterra Front had kidnapped two more of its citizens, and played a disturbing video of the captives in which they plead for their lives.

After transforming themselves into a political party and renouncing violence, the FARC have condemned the attacks by their former members. However, the new FARC have not proven as reliable a partner as Mr Santos might have hoped. On April 9th Colombian authorities arrested Seuxis Hernández Solarte, a FARC official who goes by the name Jesús Santrich and was slated to take up one of ten Congressional seats reserved for the new party in July. He was charged with conspiring to export ten tonnes of cocaine.

FARC leaders have decried his arrest as an effort to discredit their party, and demanded that he not be extradited to the United States. Relying on reports from local and American investigators, Colombian media have published stories alleging that one of the sources of the shipment in question was none other than the Oliver Sinisterra Front. Mr Santrich vehemently denies the charges. But if evidence emerges to support such links, tenuous public support for the peace deal—the first draft of which was rejected by voters in a referendum—could weaken even further. Colombia’s presidential candidates are paying close attention. Iván Duque, the front-runner, has campaigned on revising the pact to remove the FARC’s reserved legislative seats and exclude drug-trafficking crimes from the deal’s lenient special court.