The search for a missing Titanic-bound submersible has become an investigation and salvage mission that will take an indefinite amount of time, officials said, as tributes from around the world poured in for the five people killed when the vessel imploded deep in the North Atlantic.

The announcement Thursday that all aboard perished when the submersible imploded near the site of the iconic shipwreck brought a tragic end to a five-day saga that included an urgent around-the-clock search and a worldwide vigil for the vessel known as the Titan.

The investigation into what happened was already underway and would continue in the area around Titanic where debris from the submersible was found, said Rear Adm. John Mauger, of the First Coast Guard District.

“I know there are also a lot of questions about how, why and when did this happen. Those are questions we will collect as much information as we can about now,” Mauger said, adding that it was a “complex case” that happened in a remote part of the ocean and involved people from several different countries.