A Cape Town couple, wanted in the US for allegedly exploiting patients with promises of miracle stem cell cures, could have been extradited months ago.

Stephen van Rooyen and his American wife Laura Brown, who live in Llandudno, were expected to be arrested by Interpol authorities in January, soon after the Constitutional Court ruled that the extradition agreement between South Africa and the US was valid.

The couple are facing a 51-count indictment handed down by a federal grand jury in Atlanta in 2006.

Senior Superintendent Tummi Golding, Interpol's spokeswoman in South Africa, said Van Rooyen and Brown were still wanted in the US but were co-operating with the police.

"They are awaiting extradition. Arrangements are being made to re-enrol the matter but there are some legal procedural delays that need to be finalised."

Golding said extradition proceedings could take long.

Van Rooyen and Brown ran a Hout Bay-based company called Advanced Cell Therapeutics, which allegedly charged people thousands of rands for stem cell treatments using cells that should not have been injected into people.