Investigators in Tennessee will announce "new and significant developments" in the Holly Bobo murder case on Tuesday, CBSNews.com reported.

Bobo, a 20-year-old nursing student, disappeared on April 13, 2011 from her Decatur County home. Though her body was never found, authorities arrested Zachary Adams, 29, in February after new leads.

Adams faces kidnapping, first-degree murder, and witness coercion charges and has pleaded not guilty.

A meeting of the Decatur County Grand Jury has reportedly been ordered, meaning there could be new charges filed in the case. However, it is not known who the new charges would be filed against.

According to WRCB-TV, the charges will be filed against a second unidentified person.

Tennessee Bureau of Investigation Director Mark Gwyn and District Attorney General Hansel McCadams will discuss new details at 5 p.m. from the Decatur County Sheriff's Office.

It was not until earlier this month that Adams was charged with witness coercion after allegedly threatening his brother, who is in prison on firearms charges, to stay silent about the crime.

An inmate told TBI investigators that when Adams learned he was being transferred to another prison -- where his brother, John Dylan Adams, is serving his term -- he asked him to send a message to his brother: "He's the one who started this s*** and if he don't shut his mouth he will be in the hole beside her," according to CBS News.

A motive for the kidnapping and murder has not been disclosed by authorities yet.