An artist's impression of a suspect in Madeleine's case has been released
Retired British detectives are following up "potentially significant" information about the disappearance of Madeleine McCann, a spokesman has said.
Clarence Mitchell, representing the McCanns, said at least 50 calls were received after a documentary about Madeleine was aired on Channel 4.
Viewers saw an artist's impression of a man believed to have been watching the McCanns' Portuguese holiday home.
Madeleine was three when she vanished from the Algarve resort two years ago.
Her parents, Gerry and Kate McCann, from Rothley, Leicestershire, are employing two retired British policemen to continue the search for their daughter.
Clarence Mitchell told the BBC: "We're very pleased, the detectives are very encouraged by the fact that a lot of information has come in.
"We've had at least 50 calls after the Channel 4 documentary alone and there is potentially significant information in all of those calls - they're all being checked out.
A computer-aged picture (right) shows how Madeleine (left) may look now
"We've had a number of possible sightings of Madeleine; again, where there is credible information, they're being checked out.
"The good thing is some of this information is now coming from Portugal which is where the detectives helping Kate and Gerry believe the answer may well lie."
To coincide with the second anniversary of Madeleine's disappearance this week, the McCanns released a new photograph of what their daughter could look like now and appeared on the Oprah Winfrey show in the US.
Hundreds of calls followed, including details of 30 possible sightings, mostly in the US and Latin America, and a few in Europe.