The emails relate to a government worker that has been charged in a Los Angeles County corruption probe.
If the allegations prove true, the gifts would likely violate NCAA rules, which prohibit student-athletes from receiving benefits not available to other students.
USC opens the season at home against Hawaii on Saturday.
The allegations against McKnight came from emails sent by Scott Schenter, a former Los Angeles County appraiser, and obtained by the newspaper through a public records request.
Schenter has been charged with falsifying records in order to give wealthy L.A. County residents lower property taxes.
USC told the Times that they reported the allegations to the NCAA upon being informed by the newspaper.
"We are dedicated to playing and competing the right way," athletic director Pat Haden told the newspaper.
Schenter is a key player in an investigation into whether or not county assessor John Noguez's office gave property tax breaks to wealthy citizens in exchange for campaign contributions.
McKnight allegedly received a Chevrolet Monte Carlo and a $625 plane ticket from Los Angeles to New Orleans while at USC.
Emails also point to Schenter allgedly giving USC basketball player Davon Jefferson $3,700 in cash.