COPENHAGEN (Reuters) - Finland's customs office said on Thursday it had no grounds to pursue a criminal investigation against the crew of the Eagle S oil tanker over the ship's Russian fuel cargo.

Finnish police last month seized the tanker and said they suspected the vessel had damaged a Finnish-Estonian power line and four telecoms cables by dragging its anchor across the seabed.

The customs office has separately impounded the cargo of unleaded petrol and diesel, and reiterated on Thursday that these are classified as products subject to sanctions against Russia.

But as the ship entered Finnish territorial waters at the request of Finnish authorities, the crew could not be considered to have intentionally violated the sanctions legislation, the customs office said in a statement.

"The cargo of the ship will remain detained by Finnish Customs for the time being," it added.