Special counselor Robert Mueller added a top New York prosecutor to his team investigating Russian meddling in the 2016 election who also happened to be an official who worked for fired U.S. Attorney Preet Bharara.

Assistant U.S. Attorney Andrew Goldstein of the Southern District of New York has been selected to join the probe, according to multiple reports late Friday.

Goldstein worked as the top public corruption prosecutor under Bharara, an NBC News report said. Bharara was fired in March by Trump along with 46 other U.S. attorneys and has been critical of the president ever since.

Trump has previously questioned the independence Mueller's investigation because it includes people who backed his Democratic opponent in the 2016 campaign, Hillary Clinton. "I can say that the people that have been hired are all Hillary Clinton supporters," Trump said in a recent "Fox and Friends" interview. At least three lawyers Mueller has hired to help conduct his investigation have donated almost exclusively to Democrats, including Clinton.

Also moved to Mueller's probe are investigations previously being handled in New York, including one into former Trump campaign manager Paul Manafort, a person familiar with the matter told NBC News.

Mueller's investigation also includes a look into whether Trump committed obstruction of justice, according to a Washington Post report.