CHESTERFIELD, Mo. (December 7, 2012)--Pfizer Inc.'s medical research lab in St. Louis County, Mo., is missing $700,000 worth of gold dust, and police are trying to determine whether it was lost or stolen.

Chesterfield police began an investigation this week after a Pfizer employee who was conducting inventory couldn't find the gold dust, which was purchased last year for use in research.

Police Capt. Steven Lewis said no one is "sure if they just didn't account for it and it was used naturally, or if it was stolen or misplaced."

Pfizer said in a statement it is working with law enforcement and takes the matter seriously.

It wasn't clear what purpose the gold dust has in Pfizer's research.