Former President Donald Trump speaks at the Conservative Political Action Conference at the Hilton Anatole on August 6, 2022, in Dallas, Texas.
CNN  — 

Former President Donald Trump’s legal team turned over more materials with classified markings and a laptop belonging to an aide to federal prosecutors in recent months, multiple sources familiar with the investigation told CNN.

The Trump attorneys also handed over an empty folder marked “Classified Evening Briefing,” sources said.

The previously undisclosed handovers – from December and January – suggest the protracted effort by the Justice Department to repossess records from Trump’s presidency may not be done.

The Trump attorneys discovered pages with classified markings in December, while searching through boxes at the former president’s Mar-a-Lago residence. The lawyers subsequently handed the materials over to the Justice Department.

A Trump aide had previously copied those same pages onto a thumb drive and laptop, not realizing they were classified, sources said. The laptop, which belonged to an aide, who works for Save America PAC, and the thumb drive were also given to investigators in January.

Special counsel Jack Smith’s investigation, which is pursuing possible criminal charges related to Trump’s handling of national security records and obstruction of justice, had subpoenaed Trump last May for all classified records in his possession.

FBI agents seized classified documents and other presidential records during a search last August. The Trump team also found additional documents in a Florida storage facility and turned them over to the FBI.

The discovery of two documents with classified markings in the storage unit was made after a team hired by Trump’s lawyers searched it along with three other Trump properties: Trump Tower in New York, the Bedminster golf club and an office location in Florida.

Those four searches came amid lingering concerns from the Justice Department that not all of the documents from Trump’s time in the White House had been returned to the federal government.

CLARIFICATION: This story has been updated to more clearly describe what the Trump team turned over to investigators.

CNN’s Katelyn Polantz contributed to this report.