U.S. agents on Tuesday arrested two members of the immediate family of powerful Venezuelan first lady Cilia Flores in a move that could further taint Washington's strained relationship with the South American country and with Flores' husband, President Nicolás Maduro.

Efraín Antonio Campo Flores and Francisco Flores de Freitas, the first lady's adopted son and nephew, respectively, were taken into custody in Port-au-Prince, Haiti, and turned over to the U.S. Drug Enforcement Administration (DEA), which accused them of trying to traffic 800 kilograms of cocaine, The Wall Street Journal reported.

Campo Flores and Flores de Freitas were subsequently flown to New York, where they are scheduled to appear before a federal judge on Thursday. Maduro, who referred to Campo Flores as his stepson and categorically denied the accusations leveled against the men, slammed the arrest, as he spoke at a meeting of the U.N. Human Rights Council in Geneva, Switzerland on Thursday, El Nacional reported.

"This is not the first time that an official enforces the agendas of imperial assault against Venezuela," the president said. "Nor is it the first time that we will make those lies come down."

Campo Flores and Flores de Freitas were charged in a sealed indictment, and prosecutors say they intended to sell the cocaine in New York, an unidentified person with knowledge of the matter told The New York Times.

The investigation into the incident was led by a host of U.S. governmental bodies on the federal, state and local levels, including the DEA's Organized Crime Drug Enforcement Task Force, the Department of Homeland Security, the New York Police Department, the New York State Police, the United States Marshals Service and the Internal Revenue Service, the newspaper said.

Venezuela's consul in New York, Calixto Ortega, meanwhile, has been in contact with the DEA over the arrests, unnamed sources told The Wall Street Journal. It was not clear whether Campo Flores and Flores de Freitas had secured lawyers, the newspaper added.