Chipotle revealed this week that it discovered unauthorized activity in its credit card security system, potentially compromising customer's security.
The company says the breach was detected on the network that supports its payment systems in restaurants.
"Because our investigation is continuing," said a statement, "complete findings are not available and it is too early to provide further details on the investigation."
Tuesday, the chain said it had taken steps to re-secure its network and believe the measures were successful.
Card transactions at restaurants from March 27 through April 18 are being reviewed, Chipotle says.
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