(Adds dropped word in second paragraph to clarify Krebs was interviewed)

WASHINGTON A U.S. special counsel investigating former President Donald Trump and efforts to overturn his 2020 election loss are examining his firing of a cybersecurity official whose office said the vote was secure, the New York Times said on Wednesday.

Special Counsel Jack Smith, who is also probing Trump's handling of classified documents, has subpoenaed former Trump White House staff as well as interviewed Christopher Krebs, who oversaw the Cybersecurity and Infrastructure Security Agency under Trump, the Times said, citing unnamed sources familiar with the matter.

Trump fired Krebs in November 2020, days after the CISA issued a statement calling the Nov. 3, 2020, election "the most secure in American history" at a time of the then-president's unsupported accusations the vote had been rigged.

CISA, part of the Department of Homeland Security, works to protect U.S. elections from hackers but drew Trump's ire at the time, leading Krebs to tell associates at the time that he expected to be fired.

Representatives for Smith's office declined to comment on the report. Representatives for Krebs and Trump could not immediately be reached for comment.

The front-runner in the race for the Republican 2024 presidential nomination, Trump has persisted in making unfounded claims of widespread election fraud and promised pardons for his supporters who attacked the U.S. Capitol on Jan. 6, 2021, in a failed effort to block congressional certification of Democrat Joe Biden's presidential victory.

Smith is leading a grand jury investigation into Trump's actions around his election loss. A special bipartisan U.S. House of Representatives committee last year urged the Department of Justice to charge Trump with multiple crimes, including inciting or aiding an insurrection.

In the state of Georgia, a county prosecutor also is probing alleged interference in the state's 2020 election with charging decisions expected by Sept. 1.

Trump also faces several other legal threats, including Smith's probe into classified documents found at Trump's personal residence in Florida after the former president left the White House in early 2021.

A New York grand jury in March indicted Trump for falsifying business records related to a hush money payment to a porn star before the 2016 election. New York's attorney general has sued Trump and his company for alleged fraud.

Trump has denied all the allegations and accused prosecutors of a political "witch hunt."

(This story has been refiled to clarify that Krebs was interviewed, in paragraph 2)

(Writing by Susan Heavey; Editing by Howard Goller)