Willie Nelson (File photo)

Authorities in the U.S. state of Louisiana have issued misdemeanor citations to country singer Willie Nelson and four others for drug possession.

Officials say they found 680 grams of marijuana and about 85 grams of narcotic mushrooms on Nelson's tour bus during a commercial vehicle inspection Monday.

Louisiana state police said in a statement that police searched the bus after detecting a strong odor of marijuana from the vehicle during the inspection.

Police say Nelson and the four others on the bus were given the citations and released. The 73-year-old Nelson, whose hit songs include "On the Road Again," has been a vocal advocate for legalizing marijuana.

Some information for this report was provided by AP and Reuters.