Authorities in Honduras said Tuesday they arrested the man they believe masterminded the killings of 19 workers at a palm plantation last month.

The killings took place in Rigores, in the restive Bajo Aguan region of Honduras, where rival gangs have fought over control of palm farms and drug trafficking routes.

Carlos Molina — also known as "El Gato Negro," or the Black Cat — is suspected of planning and providing material support for the massacre, Security Minister Gerzon Velasquez told reporters.

At least six people carried out the plot alllegedly masterminded by the 27-year-old Molina, but none of them have been apprehended, authorities said.

On the same day in mid-May, five Honduran police were killed near the border with Guatemala.

Lawmakers in Honduras recently approved a series of reforms to confront criminal violence in Honduras, where the homicide rate is 24 killings for every 100,000 inhabitants. The new measures authorize the military to participate in public security tasks and create a new anti-organized crime unit.

The reforms also open up the possibility of categorizing gangs and drug cartels as terrorist groups.

The United States has recently pressured Latin American countries to crack down on cartels and gangs.

In May, the U.S. designated two well-known Brazilian crime groups as terrorist organizations. Countries such as Mexico and Brazil, with center-left leaders, have been vocal in opposing the designations, while others like Ecuador and Honduras, helmed by right-leaning governments, have supported them. In December, Trump-backed candidate Nasry Asfura won Honduras' presidential election.

Last week, Guatemala denied reports it had agreed to joint strikes with the U.S. on drug traffickers in the country, but admitted it requested Washington's help in its fight against cartels.

American commandos recently joined Ecuadorian troops in a joint mission aimed at dismantling a suspected criminal hub operated by an alleged narco-terrorist organization along the country's coast.