(CNN) -- Two separate people came up with the same name in response to computer-generated sketches of a man whom London's Metropolitan Police are working to identify in possible connection with the disappearance of then-3-year-old Madeleine McCann, the case's lead investigator revealed Monday.
The two people had phoned in the same name based on the sketches, Detective Chief Inspector Andy Redwood said during the BBC's "Crimewatch" program, which aired an appeal Monday night for information about a man police want to track down. The man was seen carrying a child matching McCann's description on the night she vanished in 2007 around the resort town of Praia da Luz in Portugal.
The man is described as white, between 20 and 40 years old, with short brown hair and a medium build. He was seen carrying a blond child, who might have been in pajamas and who was estimated to be 3 to 4 years old, around the time Madeleine disappeared, police had said.
The sketches are based on descriptions from separate witnesses, investigators said.
Since the program aired, British police said they have received more than 300 phoned tips and 170 e-mailed ones.
"We will now take the time to follow up these lines of enquiry," Redwood said.
The latest revelation is critical in reconstructing what exactly happened more than six years ago on the night of May 3, 2007,when McCann disappeared from her family's villa while her parents dined at a nearby restaurant. The girl was just days shy of her fourth birthday.
Neither her parents nor the detectives investigating her case have given up on one day finding the little girl from Leicestershire, England.
"There may be an entirely innocent explanation of this man, but we need to establish who he is to assist with our inquiries," Redwood said earlier.
Additionally, investigators believe they have a better understanding of when Madeleine may have been abducted, Redwood added.
"The timeline we have now established has given new significance to sightings and movements of people in and around Praia da Luz at the time of Madeleine's disappearance."
Police announced in July that they have identified 38 "people of interest" in connection with the case. Twelve of them are UK nationals who police say they think were in Portugal at the time the girl went missing. All the others are European nationals.
Metropolitan Police officers have also been talking to authorities in other countries to get more information about them and their potential involvement, the statement said.
Meanwhile, Madeleine's parents continue to keep hope that their daughter will be returned to them, explaining on their website: "We still worry about her, we miss her as much as we ever did, we remain as determined as ever to find her and to know what has happened."
CNN's Erin McLaughlin and Stephanie Halasz contributed to this report.