The 48-year-old from Switzerland was last seen at around 2pm on Saturday 22 July aboard the Condor Clipper as it was sailing across the English Channel.
Police say the vessel was still in UK waters at the time.
ITV News understands that some of Ebla's possessions were found on board the ferry and that she was travelling alone to Jersey.
On Thursday 27 July, the Channel Islands' police forces issued a joint statement confirming her identity.
It said: "There is nothing to indicate that Ebla disembarked in Guernsey or Jersey, and after arrival in Jersey the crew conducted a full search of the boat and Ebla was not found."
Officers are looking to speak to anyone who may have spoken to her before or during the sailing, saying "any information could assist the ongoing search".
Guernsey's harbour master previously said the passenger is "believed to have fallen overboard", but the police investigation into her disappearance is still ongoing.
Anyone with information is asked to call Jersey Police on 01534 612612 or Guernsey Police on 01481 222222.
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