Two nephews of Venezuela’s powerful first lady, Cilia Flores, have been arrested in Haiti on charges of conspiring to smuggle 800 kilograms of cocaine into the US, two people familiar with the case said on Wednesday.

The incident is likely to heighten tensions between the US and Venezuela and cast a new look at US accusations of drug trafficking at the highest levels of embattled President Nicolás Maduro’s socialist administration.

The two arrested men, identified as Efraín Campos and Francisco Flores, were detained on Tuesday night when they arrived on a private plane in Haiti’s capital, Port-au-Prince, said Michael Vigil, the former head of international operations at the Drug Enforcement Administration, who was briefed by US authorities about the lengthy undercover operation that led to their capture.

Vigil said Campos claimed to law enforcement that he is the son of Flores and stepson of Maduro. Both Campos and Flores were traveling on diplomatic passports but do not have diplomatic immunity, Vigil said.

Another person briefed on the incident, who agreed to talk about the case only if not quoted by name, said Campos is the son of a deceased sister of Flores and was partly raised by the first lady and Maduro.

That person said the two men had already been extradited from Haiti, whose government is a close ally of Maduro, and would be arraigned on Thursday in US district court in New York.

Flores, who Maduro likes to call the “first combatant”, is one of the most powerful members of Venezuela’s revolutionary government and a constant presence alongside her husband whenever he appears in public.

A former president of the national assembly who is now running for congress in elections three weeks away, she became romantically involved with Maduro in the 1990s while serving as lawyer for the then jailed Hugo Chávez. Maduro was one of many leftist activists drawn to the charismatic junior army officer following his arrest for a failed 1992 coup attempt. Maduro and Flores formally wed in 2013 shortly after Maduro was elected president.

Venezuela’s communications ministry and foreign ministry declined to comment about the reported arrests, saying they had no information about the incident.

Maduro and Flores traveled this week to Saudi Arabia to attend a summit of South American and Middle Eastern leaders. Maduro was expected to address the United Nations Human Rights Council on Thursday at a special meeting in Geneva called at his request.

American prosecutors have been steadily stepping up pressure on high-ranking members of Venezuela’s military, police and government officials for their alleged role in making the country an important transit zone for narcotics heading to the US and Europe. The US government says more than 200 tons a year of cocaine flows through Venezuela, about a third of Colombia’s estimated production.

But while several Venezuelan officials, including a former defense minister and head of military intelligence, have been indicted or sanctioned in the US, and many more are under investigation, no drug case had previously touched Maduro’s inner circle.

The arrests come as Maduro’s government is reeling from an economic crisis marked by triple-digit inflation and widespread shortages that have emboldened its opponents. Polls say Venezuelans could hand the ruling socialist party its biggest electoral defeat in 16 years in next month’s legislative elections.

Vigil said negotiations between the two arrested men and an undercover agent focused on getting a plane and pilot to fly the drugs to Honduras, a popular smuggling destination for cartels operating in Venezuela, for their eventual transport to the US.

The other person briefed on the case said abundant photographic and video evidence was collected as part of the sting. Venezuela’s consul in New York, Calixto Ortega, called the State Department on Wednesday to lodge a protest, the person said.