Pfizer Inc.’s medical research lab in St. Louis County is missing $700,000 worth of gold dust, and police are trying to determine if it was lost or stolen.

Chesterfield police began an investigation this week after a Pfizer employee doing inventory couldn’t find the gold dust purchased last year for use in research.

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.