London (CNN) -- Police investigating the disappearance of three-year-old Madeleine McCann from a holiday apartment in Portugal in 2007 say they are hunting a man who assaulted five other British girls in resorts on the Algarve between 2004 and 2006.
The announcement is the latest development in a long-running and controversial hunt for the missing girl.
When and where was Madeleine last seen?
Madeleine McCann was a few days shy of her fourth birthday when she vanished from her family's holiday apartment in the Portuguese resort of Praia da Luz on May 3, 2007.
Her parents, Kate and Gerry, had left Madeleine and her younger twin siblings, Sean and Amelie, asleep while they went for dinner with friends at a tapas restaurant nearby.
Kate McCann raised the alarm at about 10pm that evening when she returned to check on the children and discovered that Madeleine was missing; the window of the children's room was open.
What happened next?
The case sparked worldwide interest, boosted by a massive publicity campaign launched by the McCanns, who are doctors from Leicestershire in central England.
A large reward was offered for information on Madeleine's whereabouts, including contributions from "Harry Potter" author J.K. Rowling, pop mogul Simon Cowell, and businessman Richard Branson.
The McCanns traveled widely to publicize the search for their daughter. The couple, who are Roman Catholics, also met the then-Pope Benedict XVI in Rome to ask him to pray for Madeleine's safe return.
Who were the early suspects in the case?
Portuguese police named Robert Murat, a British man living in Portugal, as an "arguido", or official suspect, some 10 days into the investigation; Murat denied the allegations and insisted he was innocent.
In September 2007, Kate and Gerry McCann were themselves named as suspects by Portuguese investigators, amid reports DNA had been found in a car they rented weeks after Madeleine vanished. They strenuously denied the allegations, and Portuguese police closed the case against them in July 2008.
The couple accepted $1.1m in libel damages, and secured front page apologies from UK newspapers the Daily Star and Daily Express over reports suggesting they were involved in their daughter's disappearance.
In 2011, Kate McCann told the Leveson Inquiry into theconduct of the British press that she felt "violated" by media coverage of the case, in particular the publication of extracts from her diary in the now-defunct News of the World. Gerry McCann told Leveson that the paper's editor verbally beat the couple "into submission" to make them take part in an interview.
What happened after the case was closed in 2008?
Portuguese investigators turned their files over to the McCanns' private detectives, who continued to follow up potential leads and tip-offs, while the McCann family and their supporters pressed UK authorities to open an investigation of their own into the case.
In October 2013, British police issued new police sketches of potential suspects in the case, along with new lines of inquiry linked to a series of burglaries in the resort where Madeleine went missing.
Police in Portugal later said they would reopen the case.
Have there been any sightings of Madeleine?
What do Madeleine's parents believe happened to her?
Kate and Gerry McCann believe Madeleine was kidnapped, and that she is still alive somewhere. The couple regularly appeal for information on her whereabouts.
In May 2009, two years after Madeleine vanished, Kate McCann told U.S. TV presenter Oprah Winfrey that she was keeping Madeleine's room ready for her, and that she visited it twice daily, "just (to) say hello ... just (to) tell her we're still going ... to do everything we can to find her."
What are the latest developments?
On March 19, 2014, British police said they were hunting a man who assaulted five other young British girls on holiday in Portugal in the years leading up to and following Madeleine's disappearance.
Officers are now investigating a dozen potentially linked crimes at resorts near where the three-year-old vanished.
In each of the cases, a man described as tanned and with short, dark, unkempt hair, is suspected of breaking in to vacation homes where British families were staying in the Algarve.
In four of the incidents, girls between 7 and 10 years of age were sexually assaulted in their beds.