The first company to publicly announced that they had clone a human have now said that they did it again, successfully growing an embryo until it was in its 16-cell stage.

Advance Cell Technology, based in Massachusetts, made the announcement yesterday, adding that they had also created multiple embryos using the parthenogenesis which needs only a human egg - no sperm or cloning.

Medical Director for Advance Cell Technology, Dr. Robert Lanza, said of the repeated success: "It's not a scientific advance." ACT hopes its research will lead to more advanced medical treatments by using stem cells.