By Vivian Sequera and Matt Spetalnick

CARACAS/WASHINGTON (Reuters) -U.S. hostage affairs envoy Roger Carstens and U.S. Ambassador James Story traveled to Caracas on Monday for talks with Venezuelan officials about American citizens held there, a U.S. State Department spokesperson said.

A previous visit by Carstens in March as part of a high-level U.S. delegation led to the release of two detained Americans, but at least eight U.S. prisoners remain.

Venezuelan President Nicolas Maduro disclosed Monday's visit, saying U.S. officials met with the head of the government-controlled congress, Jorge Rodriguez, to continue talks that began in March. But he did not provide details.

Sources familiar with the matter said the agenda for Monday's talks was limited to humanitarian issues and did not include the country's oil, which has been under U.S. sanctions since 2019.

In March, a high-level delegation from the United States met with Maduro at the government palace, and easing U.S. sanctions was among the topics discussed, although no agreement was reached at the time.

That visit marked the highest-level U.S. talks with Caracas in years, and Venezuela soon freed a former Citgo executive and a Cuban American and also promised to resume election talks in Mexico with the opposition.

Maduro has yet to agree on a date to return to the negotiating table.

Five other Citgo executives are still held in Venezuela.

Also in custody is Matthew Heath, a Marine veteran charged with terrorism and arms trafficking. Heath, who has denied the charges, remains in a Venezuelan hospital after what his lawyer said was an attempted suicide by cutting his own arm last week.

U.S. officials said Heath was not sent by Washington and have accused Venezuelan authorities of holding him illegally.

Two other Americans still detained are former U.S. special forces members, Luke Denman and Airan Berry, who were arrested in 2020 in connection with a botched raid aimed at ousting Maduro.

The State Department spokesperson said the latest Caracas visit was "for discussions about the welfare and safety of U.S. nationals in Venezuela." The official did not immediately respond to a query on whether any Americans were expected to be freed during the latest visit.

The U.S. delegation also met with Venezuelan opposition leader Juan Guaido. Washington recognizes him as Venezuela's legitimate interim president, having rejected Maduro's 2018 re-election as a sham.

March's delegation was led by U.S. President Joe Biden's top Latin America adviser Juan Gonzalez, and also included Carstens and Story, U.S. ambassador to Venezuela who is based in Bogota in neighboring Colombia.

That meeting took place at a time when Washington was looking to fill the void that would soon be left by a U.S. ban on Russia's energy imports over its invasion of Ukraine.

Republican lawmakers and some of Biden's fellow Democrats who oppose any softening of U.S. policy toward Maduro blasted the U.S. approach to Venezuela as too one-sided.