The mysterious death of a harness racing horse at Cal Expo is under investigation. 

Hours after Nutmeg's Davey won a $3,000 claiming race Saturday Night, the trotter was dead and being shuffled off the grounds.  

The five-year-old was having the best season of its career -- winning six of the last seven starts.  

State racing rules say the body of the horse must be turned over to U.C. Davis Equestrian Center for a necropsy to see if there are any drugs or foreign substances in the animal's system. But Nutmeg's Davey was taken to a farm.  

The tracks operator, Watch and Wager, had to recover the body so the necropsy could be performed.  

The move has resulted in the immediate banning of the owner Ormin Carrera and trainer Dario Solares pending the investigation, they also face suspension of their racing licenses or possible criminal charges.