A federal grand jury has indicted two Lawrence residents, accusing them of conspiring to manufacture for nearly two years more than 100 marijuana plants at a residence outside Lawrence.

Prosecutors allege that Vajra A.J. Robinson, 26, and Tanna R. Hess, 30, participated in a scheme to manufacture marijuana plants from Jan. 1, 2008, to Aug. 21, 2009.

Robinson already faced a trial in the case in October when a federal jury convicted him on a gun possession charge while using drugs, but the jury was unable to reach a verdict on the conspiracy and drug manufacturing charges, according to federal court records.

This week the grand jury filed a superseding indictment against Robinson and also indicted Hess on the conspiracy and drug charges. According to records, the two defendants are accused of participating in a marijuana growth operation at a residence in the 1700 block of East 1500 Road, which is just outside North Lawrence.