Katrice Lee disappeared on her second birthday in November 1981.
CNN  — 

The UK’s Royal Military Police are starting a major forensic search on a riverbank in northwest Germany 36 years after a British toddler disappeared in the area, according to the British army.

Katrice Lee went missing from a shopping center in the city of Paderborn on November 28, 1981, her second birthday, the army said in a statement. She was out with her mother near the military base where her father was stationed at the time.

Katrice was never found despite large-scale searches of the area conducted by British and German police as well as British troops and volunteers.

Speaking to BBC Radio on Tuesday, Katrice’s father, Richard Lee, said his daughter’s disappearance was “every parent’s nightmare” and had caused “massive distress to the family.”

After reopening the investigation in 2012 and reanalyzing evidence gathered in 1981, the Royal Military Police identified the bank of the River Alme at Paderborner Strasse, a short distance from the shopping center, as being “of particular interest.”

The UK's Royal Military Police are starting a search of a riverbank this week in Paderborn, Germany.

The excavation, which is part of Operation Bute, a broad investigation into the toddler’s disappearance, is expected to last around five weeks and will be carried out by civilian forensic experts and military personnel, according to Richard O’Leary, senior investigating officer of the Royal Military Police.

“The aim of the search is to find evidence that could finally shed light on what happened to Katrice,” O’Leary said.

This age progression image shows what Katrice Lee might look like at age 38.

Investigators are also exploring other lines of inquiry, including the possibility that the child was abducted and is still alive but unaware of her true identity, according to the army statement.

Investigators have produced an “age progression image” of what 38-year-old Katrice might look like in the hope that someone may recognize her.

Police have also reissued a composite photo of a man seen at the shopping center holding a child similar to Katrice on the day the toddler disappeared and then getting into a green sedan.

A composite photo shows the image of a man seen holding a child the day Katrice disappeared.

“Thirty-six years have passed and allegiances may have changed,” O’Leary said. “We are appealing to members of the public and the military community, including veterans and retired civil servants in both Germany and the UK: Do you know what happened to Katrice?”

Anyone with information is encouraged to contact Operation Bute via the phone numbers and social-media accounts listed on this British army webpage.