Willie Nelson has campaigned for the legalisation of marijuana

The country singer and four others were charged with drug possession offences after a routine police stop near Lafayette, Louisiana.

Nelson could face up to six months in jail and an unspecified fine, Reuters news agency reported police as saying.

The 73-year-old star is known to be a long-time user of marijuana.

The singer's tour bus was stopped early on Monday morning about seven miles east of Lafayette.

Police allegedly seized one-and-a-half pounds (0.7kg) of marijuana and two-tenths of a pound (91 grams) of psychedelic mushrooms.

The other passengers were Tony Sizemore, 59; Bobbie Nelson, 75; Gates Moore, 54; and David Anderson, 50.

All were described as "cooperative" by a state police spokesman.