The parents of British toddler Madeleine McCann, who went missing while on holiday in 2007, said Friday they "welcome the news" that Portuguese authorities and German prosecutors have declared a convicted German rapist the prime suspect in her disappearance.

The girl's parents, Kate and Gerry McCann, said in a statement on their website that the announcement was a reflection of "progress in the investigation" into the "disappearance of our beloved daughter Madeleine".

"Even though the possibility may be slim, we have not given up hope that Madeleine is still alive and we will be reunited with her," they added, however.

Portuguese public prosecutors announced late Thursday that a man had been named as an "arguido", or formal suspect in the high-profile case.

While they did not name the suspect, it is understood to be Christian B., the same person German prosecutors in Brunswick are investigating on suspicion of murdering "Maddie".

No charges have been brought yet against Christian B. in either country however, and no body has been found.

The McCanns said in their statement that it "is important to note the 'arguido' has not yet been charged with any specific crime related to Madeleine's disappearance".

Christian B.'s lawyer, Friedrich Fuelscher, told AFP the Portuguese announcement "should not be overrated".

He said the "arguido" move appeared to be linked to Portugal's 15-year statute of limitation for certain crimes.

"I assume that the statute of limitations was interrupted by this step," Fuelscher said.

Brunswick prosecutor Hans Christian Wolters also suggested the step was a formality and unlikely to indicate a major breakthrough in the Portuguese probe.

"Portugal apparently by now also sees reason to suspect" Christian B., Wolters said.

But he said he would be "surprised" if the Portuguese probe was further along than the German one.

Portuguese prosecutors said they were working "in cooperation with English and German authorities".

Christian B. is currently serving a seven-year sentence in Oldenburg, northern Germany, for raping a 72-year-old American tourist in Portugal's Praia da Luz in 2005.

Madeleine McCann, then aged three, went missing from a Portuguese seaside resort on May 3, 2007
Madeleine McCann, then aged three, went missing from a Portuguese seaside resort on May 3, 2007 POOL via AFP / STRINGER

Madeleine McCann, then aged three, went missing from the same seaside resort on May 3, 2007.

Her disappearance sparked a huge manhunt and an international media frenzy, with photographs of Maddie plastered across billboards and news bulletins.

Maddie's parents Gerry and Kate were at one point also declared "arguidos" in the Portuguese investigation, before the status was lifted for both of them.

The latest step "is related to the statute of limitations", agreed ex-police inspector Goncalo Amaral, who led the inquiry into Maddie's disappearance in Portugal in 2007.

"It's a procedural trick by the public prosecutors," he said.

Amaral was sued by Kate and Gerry McCann over a 2008 book in which he accused them of concealing her body after she died accidentally.

Portuguese police shelved their controversial investigation -- which saw Amaral sacked -- in 2008, but reopened it five years later citing "new elements".

British police opened their own inquiry in July 2013, but on-site excavations in Praia da Luz yielded no evidence.

The case appeared to have gone cold until Brunswick prosecutors made the stunning revelation in June 2020 that they were certain Maddie was dead and that they believed Christian B. killed her.

Christian B. was at that time already serving a jail sentence for drug trafficking in Kiel, northern Germany.

He has a long criminal history including sex offences and convictions for child sexual abuse.

Christian B. lived just a few kilometres (miles) away from Praia da Luz in Portugal's Algarve region at the time Maddie vanished from her family's holiday accommodation, according to Brunswick prosecutors.

Wolters said his team was currently also investigating Christian B. on suspicion of raping an Irish woman in 2004 and over suspected cases of child abuse in Portugal.

Wolters said he hoped to complete those probes soon, while the Maddie investigation "could take a while longer".