Federal prosecutors have begun "informal plea negotiations" with most of the self-described Oath Keepers militia members charged in a sweeping conspiracy case involving the Jan. 6 insurrection, a prosecutor said during a hearing in the case Tuesday.

Government attorneys have started to discuss the parameters of what plea offers for the accused Oath Keepers might look like, the prosecutor said, adding that while those discussions remain informal and "preliminary at this time," the government hopes to offer formal plea deals "over the next month or two."

The development came just one day after the government indicted four new individuals, bringing to 16 the number of accused Oath Keepers facing charges in the case, which range from conspiracy and obstruction to civil disorder and assaulting officers. Joseph Hackett, Jason Dolan, William Isaacs, and another person whose name was redacted from the filing were added through a superseding indictment.

The case alleges coordination between some of the rioters who participated in the Jan. 6 attack on the Capitol, and plea deals would mark a significant step forward in the government's investigation. In total, nearly 20 self-described Oath Keepers members have been charged in connection with the riot, according to an ABC News analysis of arrest records.