"It is a serious violation of the law to try to buy concert tickets using stolen credit card information and, when successful, to resell those tickets to unknowing consumer victims through resale web sites," Ticketmaster president/COO Sean Moriarty said in a prepared statement. "With the Streisand tour, the unusually high number of incidents of fraud has prompted us to issue this specific warning. We are working closely with law enforcement to identify the source of this fraud and prosecute to the full extent of the law."

Moriarty, along with Michael Cohl, who is the tour's national promoter, and Matrin Erlichman, Streisand's manager, are warning fans that, if they purchased tickets from a reseller, their tickets may not be valid.

"With the overwhelming number of cancelled tickets accessible for sale in the secondary market, it's imperative that we warn consumers that Barbra Streisand tickets purchased from unauthorized resellers may not work at the door on the night of the show," Cohl said in a statement. "The only way for fans to know that their tickets are valid is to purchase their tickets from venue box offices or from Ticketmaster, the venues' authorized ticketing company. We're hoping this warning will help to protect fans not only from losing their money, but also from missing the opportunity to attend a concert they've waited so long to see."

A list of exactly which tickets have been invalidated is available at Ticketmaster's Barbra Streisand ticketing page.

As previously reported, Streisand is ending a decade-plus touring hiatus with a fall outing that launches Oct. 4 in Philadelphia. Details appear below.