The Justice Department said in a December letter to the secret court that oversees surveillance of suspected foreign spies that it lacked probable cause to continue surveillance of Mr. Page in two of the four surveillance applications it sought against him.

The government began surveillance of Mr. Page in late 2016, after he left the Trump campaign. It ultimately obtained a warrant and three subsequent renewals.

The Justice Department now appears to have concluded that there was “”insufficient predication to establish probable cause” in the last two renewals in 2017. Probable cause is the legal standard to obtain a secret warrant against suspected agents of a foreign power. The letter is classified, but is referenced in a new order declassified by a judge on Thursday. The Justice Department said it would sequester all the material it collected against Mr. Page pending further internal review of the matter.