Special counsel Robert Mueller's federal grand jury has been extended for up to six months.

The grand jury, based in Washington, DC, was seated for an 18-month term that began in July 2017 and was set to expire in the coming days.

Under federal rules, the court is able to extend a grand jury's term for another six months if it is "in the public interest."

Grand jury activity is secret, except following the 23-person group's approval of criminal indictments.

Chief Judge Beryl Howell of the DC District Court, who oversees the Mueller grand jury, granted the extension. She does not sit in on its sessions.