Police in Germany have begun searching an allotment near Hanover as part of the continued investigation into the disappearance of British girl Madeleine McCann, the public prosecutor's office has said.

Madeleine disappeared 13 years ago from an apartment in Portugal while her family vacationed in the seaside town of Praia da Luz.

She was just three years old when she went missing.

Julia Meyer, a spokeswoman for the prosecutor's office in Braunschweig confirmed local media reports that police had been at the garden plot site since Monday.

They have been using excavators at the site and sniffer dogs were used on the grounds but police have not yet explained exactly what they are looking for.

German authorities said last month they had identified a 43-year-old German man — identified in local media as Christian B — as a suspect in the McCann case and are investigating him on suspicion of murder.

The suspect, who is currently in prison in Germany, spent many years in Portugal, including in Praia da Luz around the time of Madeleine’s disappearance, and has two previous convictions for "sexual contact with girls," authorities have said.

Last month German prosecutors said they had evidence Madeleine was dead but needed more information about where Christian B had lived so they could search for her body.

Hans Christian Wolters, from the Braunschweig public prosecutor's office, also said he did not have enough evidence currently for the suspect to go on trial.

AP