US authorities on Friday dismissed accusations that a French researcher had been barred entry to the United States because of his political opinions, stating that he had confidential material from a nuclear research laboratory.

The French government reported on Wednesday that the researcher had been denied entry while attempting to attend a scientific conference in Texas. "This measure was apparently taken by the American authorities because this researcher's phone contained exchanges with colleagues and friends in which he expressed a personal opinion on the Trump administration's research policy," said Philippe Baptiste, France’s Minister of Higher Education and Research.

However, a spokesperson from the Department of Homeland Security contradicted these claims, declaring to the foreign news agency, "Any claim that his removal was based on political beliefs is blatantly false."

The spokesperson added, "The French researcher in question was in possession of confidential information on his electronic device from Los Alamos National Laboratory – in violation of a non-disclosure agreement – something he admitted to taking without permission and attempted to conceal."

The Los Alamos National Laboratory, based in New Mexico, was established by Robert Oppenheimer during World War II to develop the atomic bomb and continues its research on nuclear weapons.

A French diplomatic source revealed that the researcher was randomly checked upon his arrival, with his work computer and personal phone being searched. He was allegedly accused of posting messages "that convey hatred toward Trump and can be classified as terrorism." His professional and personal devices were seized, and he was sent back to Europe on March 10.

Since Donald Trump returned to the White House, he has been known for his targeting of the scientific community, reducing research budgets, imposing restrictions on universities, and censoring certain topics in funded research.

The French Academy of Sciences on Friday called for international scientific organisations to "denounce an authoritarian drift that is harmful to science."