BERLIN (AP) — Scientists in Europe say they've successfully transferred a test tube rhino embryo back into a female whose eggs were fertilized in vitro, as part of an effort to save another nearly extinct sub-species of the giant horned mammal.

Thomas Hildebrandt of the Leibniz Institute for Zoo and Wildlife Research in Berlin said Tuesday the procedure was performed last month on a southern white rhino at Chorzow Zoo in Poland.

Hildebrandt is part of an international team trying to save the northern white rhino. The team is hoping to get permission from Kenya to harvest eggs from the last two surviving female northern white rhinos soon.

He told reporters that "this is the first positive proof that the entire procedure we've developed in theory can be successful."