Lil' Wayne, whose real name is Dwayne Carter, and the others were questioned and released, according to U.S. Customs and Border Protection, and the case was referred to the Brooks County Sheriff's Office.
A sheriff's spokeswoman told The Associated Press that she could not comment.
The tour buses were stopped in Falfurrias, about 80 miles southwest of Corpus Christi, where the rapper is scheduled to perform Sunday night.
Lil' Wayne played in Hidalgo on Thursday. A few minutes before the doors were to open for his show in Laredo on Friday, it was announced that the show was postponed. A marketing manager for the venue told the Corpus Christi Caller-Times that it would be rescheduled.
A drug dog initially detected the odor of narcotics on one of the buses, the CBP said in a news release. Marijuana was found during secondary inspections, the agency said.
Lil' Wayne's music manager Cortez Bryant and talent agent Cara Lewis did not immediately return phone messages left at their offices.
The rapper pleaded guilty in October to attempted criminal possession of a weapon in a New York case, a charge that stemmed from a 2007 traffic stop of his tour bus. His plea deal calls for a year in jail in that case. He is set to appear for sentencing in February.