German prosecutors believe missing British girl Madeleine McCann is dead.
They said on Thursday that a murder probe had been opened after a new suspect had been identified in the case.
McCann, then three, went missing on May 3, 2007, in and around the resort in Praia da Luz, on Portugal's Algarve coast.
The German man has not been named but the Metropolitan Police said he is 43 years old and had been in and around the resort at the time of her disappearance.
In its public appeal for information, the police described the suspect as having "short blond hair, possibly fair" and being "about 6ft in height with a slim build".
They also provided information regarding a "VW T3 Westfalia campervan" registered in Portugal, which the suspect is believed to have used in and around the Praia da Luz resort at the time of McCann's disappearance.
"We believe he was living in this van for days, possibly weeks, and may have been using it on 3 May 2007," the police said.
A second vehicle, "a 1993 British Jaguar, model XJR 6, with a German number plate", was also identified by the police as located in the Praia da Luz area in 2006 and 2007 and was registered in the suspect's name in Germany.
"On 4 May 2007, the day after Madeleine’s disappearance, the car was re-registered to someone else in Germany," police said.
The suspect is currently in prison in Germany for an unrelated matter, they added. According to Germany’s Federal Criminal Police Office, he was jailed for a sexual crime.
The man, a German citizen who was 30 at the time of McCann's disappearance, lived "on and off in the Algarve between 1995 and 2007".
The German Federal Criminal Police said that he had several occasional jobs during that time and "also earned his living by committing criminal offences, such as burglaries of hotel complexes and holiday flats as well as trafficking in narcotic drugs".
Madeleine McCann vanished just before her fourth birthday. She was last seen asleep in her family's holiday apartment with her twin siblings. Her parents dined with friends at a restaurant nearby and she was gone upon their return.
“It’s more than 13 years since Madeleine went missing and none of us can imagine what it must be like for her family, not knowing what happened or where she is," Detective Chief Inspector Mark Cranwell, who leads the British police's Operation Grange in search of McCann, said.
“Following the 10-year anniversary, the Met received information about a German man who was known to have been in and around Praia da Luz."
Authorities from Britain, Germany and Portugal published a new joint call for information on Wednesday.
They are asking for any information related to the two vehicles and two phone numbers, +351 912 730 680 and +351 916 510 683, that shared a call on 3 May 2007 in the area and around the time of McCann's disappearance. The first one has been identified as the suspect's phone number at the time.
Cranwell said the British police has been working with the German and Portuguese police since they were tipped off about this suspect following a 2017 appeal for information.
In Germany, the police are treating the McCann case as a murder investigation; in the UK the Metropolitan Police continues to treat her disappearance as a "missing persons inquiry", Cranwell said.
"While this male is a suspect we retain an open mind as to his involvement and this remains a missing person inquiry," Cranwell said.
The girl's parents, Kate and Gerry McCann, said on Wednesday they welcomed the new information appeal.
"All we have ever wanted is to find her, uncover the truth and bring those responsible to justice," they said in the Metropolitan Police's statement.
"We will never give up hope of finding Madeleine alive but whatever the outcome may be, we need to know, as we need to find peace."
Madeleine McCann would be 17 years old today.