Officials say gunmen from a group known as "Los Rastrojos" stormed the "Espana" farm on Wednesday when workers were finishing up their day picking fruit. After trying to extort them, they opened fire and tossed a grenade at the laborers.
"We had never seen a massacre like this," said William Alvarez, a 56-year-old coffee farmer who knew four of the workers killed. "They were decent, hard-working people."
The funeral procession was led by Sergio Fajardo, the governor of the state of Antioquia, who shed tears as he walked into the cathedral for a service attended by more than 500 people. Many more crowded the city's main square, where a day before about 150 farm workers had gathered to seek shelter fearing a new attack.
It was the first major massacre in Colombia since August 2009, when 12 members of the Awa indigenous tribe were killed in southwestern Narino state. At the time, a prosecutor investigating the case said the killings had been committed by Los Rastrojos.
The group is a violent offshoot of the Norte del Valle cartel involved in drug trafficking, extortion and murder as it competes with other criminal bands that grew out of far-right militias known as paramilitaries.
Colombian police say the gang, which is thought to have hundreds of members, operates on Colombia's Pacific coast and along the border with Venezuela.
Several leaders of the Rastrojos were captured last week in the area and officials are blaming the group for the latest bloodshed.
Antioquia police Gen. David Guzman said that 120 policemen and soldiers are guarding the city.
"(Farm laborers) are afraid. Who wouldn't be afraid with the massacre of 10 peasants?" Guzman said, adding that authorities are prepared and can guarantee their security.
Although Guzman said the murder investigation is on the right track, he declined to provide details. Authorities are offering a $275,000 reward for information leading to the whereabouts of the killers.
Local officials say the owner of the farm was apparently being extorted by the paramilitary group.
Officials have arrested about 2,600 extortionists so far this year, according to the police anti-kidnapping unit. About 60 percent of them are common criminals and the rest belong to guerrilla groups or organized criminal gangs.
Associated Press writer Cesar Garcia in Bogota, Colombia, contributed to this report.
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