Hundreds of customers at Dollar Tree discount stores have reported money stolen from their bank accounts due to unauthorized ATM withdrawals.
The Secret Service is leading a major investigation into the allegations, which arose from stores in Carmichael, Modesto and elsewhere.
The Secret Service offered few details about the case, but one spokesman said "it's big."
A Dollar Tree spokesman also would not comment, but stated, "We are cooperating with local authorities in this situation."
A Dollar Tree store on Manzanita Avenue in Carmichael is believed to be one location in the West where a suspected fraud operation has resulted in customer financial data being stolen and used for theft.
One customer claimed that after shopping at Dollar Tree, her ATM account number and PIN number were somehow stolen and then used to take $700 from her account. Her bank, Golden 1 Credit Union, reported that about 30 customers have reported similar thefts.
A Dollar Tree store in Modesto is being investigated after 150 customers reported money taken from their accounts after shopping at the store.
KCRA 3 has learned similar data thefts occurred at a Dollar Tree store in Ashland, Ore., during May and June.
The Secret Service would not comment on whether other Dollar Tree stores are involved.
Authorities are looking at how thieves managed to get the data stored in the magnetic strips on customers' ATM cards.
In Oregon, Medford police report that theft occurred between the point of sale and the bank, with the information intercepted possibly by a theif's use of a wireless laptop computer. Officials said theives take the data and then produce new ATM cards, allowing them to withdraw cash.