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WASHINGTON — The official leading the Justice Department's investigation into whether President Donald Trump's campaign had ties to Russia's meddling in the 2016 election is leaving her position next month.

Acting Assistant Attorney General Mary B. McCord told the staff of the department's national security division this week she is leaving to pursue other opportunities.

Mary McCord Alex Wong / Getty Images file

Her departure leaves a major vacancy at a time when several key positions within the department remain unfilled. Attorney General Jeff Sessions' picks for deputy and associate attorney general — the No. 2 and No. 3 officials at the Justice Department — await Senate confirmation, and the Trump administration has not announced other top political appointees. A month after Sessions sought the resignations of the nation's U.S. attorneys, their replacements are not yet in place.

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A longtime federal prosecutor, McCord had been acting as head of the national security division since October. The unit oversees cases involving terrorism, espionage, cybercrime and other national security threats. She joined that unit in 2014 after working in the U.S. Attorney's office for the District of Columbia for 20 years.

In her memo, McCord did not reveal what she plans to do next, aside from spending time with her family.