MIAMI (AP) — Six American oil executives under house arrest in Venezuela were rounded up by police hours after President Donald Trump met Venezuelan President Nicolás Maduro's chief opponent at the White House, according to family members of the men.

Alirio Zambrano said early Friday that the executives of Houston-based Citgo were abruptly taken from their homes last night by the SEBIN intelligence police. Zambrano, the brother of two of the six detained men, said their current whereabouts are unknown.

"We demand to know they are safe but more importantly their freedom!" Zambrano said on social media, adding that he was very worried about the detainees.

The State Department and Maduro's government have yet to comment.

But the move comes two months after the men were granted house arrest and just hours after Trump welcomed opposition leader Juan Guaidó to the White House in a show of support for his flagging, year-old campaign to oust Maduro.

The embattled leader condemned Trump's embrace of Guaidó while socialist party boss Diosdado Cabello, who is widely seen as the second most powerful person in the government, vowed to retaliate for the meeting.

"Every time they do something, we're going to turn harder to the left and see who squeals," Cabello said Wednesday night in his weekly TV program.

The six men were hauled away by masked security agents while at a meeting in Caracas just before Thanksgiving in 2017. They had been lured to Venezuela in order to attend a meeting at the headquarters of Citgo's parent, state-run oil giant PDVSA.

The group flew out on a corporate jet. They included Tomeu Vadell, vice president of refining; Gustavo Cardenas, head of strategic shareholder relations as well as government and public affairs; Jorge Toledo, vice president of supply and marketing; Alirio Zambrano, vice president and general manager of Citgo's Corpus Christi refinery; Jose Luis Zambrano, vice president of shared services; and Jose Angel Pereira, the president of Citgo.

In recent weeks, speculation has swirled that Maduro's government may release the men in a bid to mend ties with the Trump administration, which has been aggressively pushing for his removal.

The men are awaiting trial on corruption charges stemming from a never executed plan to refinance some $4 billion in Citgo bonds by offering a 50% stake in the company as collateral.

Prosecutors accuse the men of maneuvering to benefit from the proposed deal.

But many believe the men, five of whom are naturalized U.S. citizens and the other a legal resident, are being held as political bargaining chips as relations between the U.S. and Venezuela have deteriorated. They cite as evidence of irregularities the decisions by Venezuelan Judge Rosvelin Gil to postpone 15 straight times a preliminary hearing.

U.S. Vice President Mike Pence in April called for the men's release after meeting with family members at the White House.

"We are going to stand with you until they are free and until Venezuela is free," he said at the time.

It's unclear whether Guaidó discussed the men during his meeting Wednesday with Trump. A senior U.S. official briefing reporters in advance of the visit didn't mention the detention.

Family members in the U.S. last spoke to the men Wednesday afternoon, according to a person familiar with the situation who spoke on the condition of anonymity and wasn't authorized to discuss the matter. Shortly after, the men were all rearrested during raids within a short span of one another, the person said.