WASHINGTON: Former US national security adviser Robert O’Brien has been subpoenaed by special counsel Jack Smith in his probes into classified documents found at former President Donald Trump’s Mar-a-Lago residence and efforts to overturn the results of the 2020 election, CNN reported on Thursday, citing a source. O’Brien has been asserting executive privilege in declining to provide some of the information that prosecutors are seeking from him, the CNN report added. Smith’s office did not immediately respond to a request for comment. Trump’s former acting Department of Homeland Security Secretary Chad Wolf was interviewed by Justice Department lawyers in recent weeks as part of the ongoing special counsel investigation related to 2020 election interference, the report added, citing sources. US Attorney General Merrick Garland named Smith as special counsel in November to oversee investigations of Trump, shortly after Trump said he would seek the Republican nomination for president again in 2024. The first probe involves Trump’s handling of highly sensitive classified documents he retained at his Florida resort after leaving the White House in January 2021. The second investigation is looking at efforts to overturn the 2020 presidential election’s results, including a plot to submit phony slates of electors to block Congress from certifying Democrat Joe Biden’s victory. Grand juries in Washington have been hearing testimony in recent months for both investigations from many former top Trump administration officials. Last month, Garland named a separate special counsel, Robert Hur, to probe the improper storage of classified documents at President Biden’s home and former office.