An F.B.I. intelligence memo unsealed on Wednesday offers new details on why the bureau concluded that some Venezuelan government officials were likely to have had some responsibility for a criminal gang’s actions in the United States, pitting it against other intelligence agencies in a heated dispute over President Trump’s use of a wartime law.

The memo, whose conclusions the remaining intelligence agencies have rejected, was submitted by the administration to a federal judge in Texas before a hearing on Thursday. It is part of a proliferating array of lawsuits over Mr. Trump’s use of the law, the Alien Enemies Act, to deport people accused of being members of that gang, Tren de Aragua, to a notorious Salvadoran prison without due process.

“The F.B.I. assesses some Venezuelan government officials likely facilitate the migration of TdA members from Venezuela to the United States to advance the Maduro regime’s objective of undermining public safety in the United States,” the memo said, using an abbreviation for the gang.

It added that the bureau also thinks some officials in the administration of Venezuela’s president, Nicolas Maduro, “likely use TdA members as proxies.”

The submission of the memo opens the door to greater judicial scrutiny of a key basis for Mr. Trump’s assertion that he can invoke the rarely used law to summarily deport people accused of being members of the gang. It also offers a glimpse of the claims put forth by several detained migrants that formed the basis for the F.B.I.’s assessment.