The ship and crew were chartered by the Estline shipping company, owner of the ferry Estonia that capsized on Sept. 28 killing more than 900 people.
Swedish authorities halted the Donata shortly after it sailed from Stockholm for Tallinn on Tuesday night.
The captain was seen by other officers to slur his speech and stumble while the boat was underway, the Swedish newspaper Aftonbladet reported.
The pilot alerted police and the ship was halted, the newspaper said.
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