Detective Sgt. Douglas Schaeffler, of the Richmond Heights police, said Saturday that the squad would begin by reviewing old investigative notes.
The length and breadth of the unit's investigation will depend on what it finds, Schaeffler said.
On Saturday, Heather's family gathered to remember her at a relative's home in south St. Louis. Her mother, Christine Kullorn, said she holds out hope that someone with important information about the case will come forward.
"You don't have to give your name, just give me my daughter," said Christine Kullorn, 44. "Somebody out there has got to know where she is, and if they have a heart, they'll bring her home."
Schaeffler said that the disappearance remains an active case, and that police continue to investigate tips as they come in.
He said police will soon use new technology to re-examine physical evidence taken from the apartment where Heather was last seen.
Heather disappeared from the apartment of family friends Dana Madden and Christopher Herbert while baby-sitting the couple's 2-month-old daughter. The baby was found alone and unharmed.
Over the years, police have speculated that Heather was murdered after witnessing drug activity nearby.
Schaeffler wouldn't discuss any motive, but he said police have a few working theories on what happened.
He also said police have identified someone he described as "a person of interest" who has more information about the case.
Schaeffler said he believes others with information about the case haven't come forward, perhaps because they believe their information isn't important or is already known to police.
He urged anyone with who knows anything about the case to call the Richmond Heights police.