It's not confirmed who took him or where he was taken, but the video posted by Tintori shows Lopez being driven away in a auto marked "SEBIN", an abbreviation for the Venezuelan intelligence service. This means that any US-based assets of his have been frozen, and American citizens are forbidden from conducting any business with him.
Mr Lopez was granted house arrest just last month after three years inside.
Tintori posted video that she says shows her husband being taken away.
Ledezma, the former mayor of Caracas and a prominent opposition figure, was also taken from his home by SEBIN, according to tweets from his wife and children.
The U.S. had earlier warned the socialist government there'd be consequences if Maduro went ahead with Sunday's election. The constituyente, as it is known, could set the stage for the Maduro government to totally and indefinitely consolidate its power, criminalize the opposition without limits, and usher in a new and even darker phase in Venezuela's crisis.
Cuba, Venezuela's closest ally, charged that "a well-organized global operation was under way, led from Washington, with the support of the OAS chief, aimed at silencing the voice of the Venezuelan people, and forcing them into submission with attacks and economic sanctions".
Unruhe further criticized Washington for disrupting the democratic political processes of countries that are not aligned with it, asserting that American officials want to drag Venezuela back to the colonial era.
Mnuchin called Maduro a "dictator who disregards the will of the Venezuelan people". The election received criticism from around the world, including from Venezuela's traditional allies. The new assembly is supposed to take over in the next two days. The new political assembly -installed by the political mechanisms of authoritarianism - will supersede all other political institutions in Venezuela.
Hours earlier, the US had sanctioned Maduro for undermining democracy, treating him as it has Bashar Assad of Syria, Kim Jong Un of North Korea and Robert Mugabe of Zimbabwe.
The top United Nations human rights official today expressed deep concern about the detention of two opposition leaders by Venezuelan authorities after Sunday's elections for a Constituent Assembly convened by President Nicolás Maduro.
"The bishops are unanimous in their rejection of this new assembly, and we are asking the government to reconsider", Cardinal Urosa told Venezuela news station Globovision the day before the vote.
Opposition leader Henrique Capriles, the governor of the central state of Miranda, urged Venezuelans to protest Monday against an assembly that critics fear will effectively create a single-party state.
Monday, US Treasury Department's Office of Foreign Assets Control (OFAC) added Maduro to its list of specially-designated nationals.
European Parliament chief Antonio Tajani said he had written a letter calling for action to Donald Tusk, head of the European Council which represents the 28 member states, and European Commission chief Jean-Claude Juncker.
In recent months, protesters have flooded the streets of Venezuela as clashes have turned violent, with more than 100 people killed in the chaos.
Venezuela's credit-default swap spreads spiked on Friday and remained elevated on Monday, with the probability of default within a year reaching 62%, a level last seen in February 2016.