(Bloomberg) -- Royal Dutch Shell Plc was impacted by a data security incident related to using Accellion Inc.’s file-transfer software, the energy giant said in a statement dated March 16.

An internal investigation has so far found that an “unauthorized party gained access to various files during a limited window of time,” Shell said. Some files contained personal data from Shell companies and their stakeholders, all of whom have been notified.

California-based Accellion said in January that its file transfer appliance software had suffered a security incident with less than 50 customers being affected. Since then companies including U.S. supermarket firm Kroger Co. and Australia’s corporate regulator have been revealed as victims of the breach.

Shell said there is no evidence its core IT systems were impacted as the file-transfer service is isolated from the rest of the company’s digital infrastructure.

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