There is growing pressure on District Attorney Mimi Rocah to bring the cold case investigation into Kathie Durst's disappearance four decades ago before a grand jury, but now it looks like the probe is quickly picking up pace.

News 12's senior investigative reporter Tara Rosenblum has been told that there are four prosecutors and investigators working on the case full time, and that the Cold Case Unit has conducted interviews and had discussions with at least 10 people in recent weeks.

Sources close to the investigation tell News 12 that the names on the list include Andrew Jarecki, the filmmaker behind the HBO documentary, "The Jinx," retired criminal investigator Ed Murphy, Pennsylvania businessman George Kearns, former celebrity publicist and newscaster Geraldine McInerney and six members of Kathie Durst's family.

Her siblings have long suspected that Kathie's husband, real estate baron Robert Durst, was responsible for her death back in 1982. So far, he hasn't been charged with any crime. They are hoping that will change soon following Durst's guilty verdict two weeks ago in the murder of his best friend Susan Berman in Los Angeles.

Prosecutors built their case on the theory Robert durst shot Berman to death to stop her from talking to investigators about what she knew about the disappearance of Robert Durst's missing first wife, Kathie.

There are also potential new legal problems now for Durst's current wife, Debrah Charatan. News 12 just learned that Kathie's family attorney sent a letter to the Manhattan district attorney Tuesday, morning accusing the couple of staging a sham marriage to help cover up Kathie's murder.

As for a timetable of when this decades old cold case might land in the hands of a grand jury in Westchester, sources tell News 12 that early October is the likely target date.

The attorney representing Robert Durst's wife denied all the allegations, sending in a statement that reads in part, "Ms. Charatan was never married to another person while married to Mr. Durst. It is sad that attorney Robert Abrams is misleading the McCormack family and the public. The McCormack family deserves better."

The Westchester district attorney declined to comment, calling the case an "active investigation."