LYSEKIL, Sweden — Rescuers said that the total number of people burned to death and drowned in the Scandinavian Star ferry fire disaster may never be known, and police expressed confidence today that they will find the arsonist believed to be responsible.

The ferry, sailing from Oslo to Denmark, caught fire early Saturday south of the Oslo Fjord with about 500 passengers and crew aboard. Police in Oslo confirmed that 176 people had died but suggested that the toll may eventually top 200.

In Copenhagen, officials were preparing for Wednesday's opening of a board of inquiry to explain Saturday's disaster, working on the "concrete theory that it was arson."