"He (Blanco) is there as a guest, we can confirm that", the official said.
Venezuela's information ministry, Argentina's foreign ministry and its embassy in Caracas did not immediately respond to requests for comment.
"I warn Venezuela and the worldwide community about the intention of the regime to disintegrate the national Parliament, through attacks carried out by the illegitimate Supreme Court of Justice and the National Constituent Assembly".
Venezuelan intelligence agents arrested Opposition leader Juan Guaido's congressional deputy Edgar Zambrano on Wednesday, using a tow truck to drag away his vehicle while he was still inside, Reuters reported.
Mr Guaido invoked the constitution to assume an interim presidency in January, denouncing Mr Maduro's rule as illegitimate after he secured re-election a year ago in a vote widely viewed as fraudulent.
The Trump administration blames Mr Maduro's socialist policies and government mismanagement for Venezuela's economic crunch, warning that 2 million more people are expected to flee by the end of the year if the crisis continues.
Things are under (Maduro's) control, the government seems to be saying. He also called for Venezuelans to take to the streets on Saturday for fresh protests against Maduro.
His arrest on Wednesday night was dramatic. Authorities have not confirmed where he was being detained.
Furthermore, White House officials said that although the president had an affinity for Juan Guaido, he has also "wondered aloud" about how much the United States really knows about him, and questioned whether he is really ready to take over governing the country.
"We will continue to use the full weight of the USA government to hold accountable those who subvert democracy and the Venezuelan constitutional order, and threaten the safety of the duly-elected National Assembly of Venezuela", a senior White House official said on Thursday, on condition of anonymity.
Another opposition figure, Marianella Magallanes, who had her immunity removed sought refuge in the Italian embassy.
Guaido's chief of staff, Roberto Marrero, was arrested in March. "Zambrano's arrest may be a test to gauge the response of the worldwide community before it moves against Guaido".
"The regime has kidnapped the first vice president", Mr Guaido said on Twitter.
"Investigations have succeeded in proving that General Manuel Ricardo Cristopher Figuera has been recruited by the Central Intelligence Agency for more than a year", Maduro said, adding that justice would be served on the "traitor" Figuera "sooner rather than later".