By Jim Forsyth

SAN ANTONIO (Reuters) - Authorities discovered marijuana, heroin and a loaded gun on Grammy-winning rapper Nelly's tour bus during a routine stop at a Border Patrol checkpoint in West Texas, law enforcement officials said on Thursday.

A member of the singer's entourage took responsibility for the items and was arrested after the search on Wednesday evening, while others on the bus including Nelly were released, officials said.

The checkpoint, which is not on the border, is used by the Border Patrol to check the citizenship status of motorists on Interstate 10.

The incident took place at the same checkpoint where singers Willie Nelson and Fiona Apple, rapper Snoop Dogg and actor Armand Hammer have been stopped for possession of controlled substances.

A spokesman for the Hudspeth County sheriff said the tour bus had pulled into the Border Patrol checkpoint in Sierra Blanca, Texas, about 90 miles east of El Paso, when a dog detected the presence of controlled substances.

"The agent requested all seven occupants out of the bus and conducted an inspection of the vehicle," spokesman Rusty Fleming told Reuters. "A search produced a small plastic container containing marijuana, 36 small bags containing heroin, and a loaded .45 pistol."

Fleming said all of the occupants of the bus were read their Miranda rights, and a passenger on the bus, Brian Keith Jones, admitted that the controlled substances and the weapon belonged to him.

Jones was arrested, Fleming said, adding that he did not know what charges he will face.

Nelly, 37, whose real name is Cornell Iral Haynes, is a Grammy-winning singer who has performed in several movies. Billboard magazine named him one of the top artists of the decade in 2009.

His manager could not be immediately reached for comment.

(Editing by Corrie MacLaggan and Cynthia Osterman)