Credit: ABC

A mysterious white powder was found at ABC's Dancing with the Stars studio in L.A. on late Friday.

An envelope containing "an unknown substance" was delivered to the DWTS production office, a rep for ABC tells

The powder may have been inside of a piece of fan mail addressed to Bristol Palin, 20, TMZ reports.

"Security and the Los Angeles Fire Department and Los Angeles Police Department were immediately notified. Measures were taken to secure the area and ensure the safety of personnel," the rep tells Us.

The substance was later determined to be talcum powder. The FBI is now handling the investigation.