Washington - A federal grand jury in Washington D.C. on October 27 approved the first charges in the investigation led by special counsel Robert Mueller, CNN reported.

But it remains unclear of who are being charged nor what are the charges, according to CNN. The report added that plans were prepared Friday for anyone charged to be taken into custody as soon as Monday.

A spokesperson for the special counsel's office declined to comment.

Mueller was appointed to lead the investigation into the role of Russia in 2016 presidential elections. The investigation covers a wide range of issues, including the firing of former FBI director James Comey.

Mueller’s team subpoenas several people worked for Donald Trump’s campaign during the presidential elections and lobbying firms related to former national security advisor Michael Flynn.

The special counsel's investigation was considered a high-profile one in the US as it relates to “potential collusion between the Trump campaign and Russia”, though the Kremlin has denied the allegations.