These hybrid embryos developed into blastocysts - the stage of development at which the researchers could implant them into a female.
Scientists developed a hybrid embryo by combining the sperm of the northern white rhino and the egg of the southern white rhino, which population is now estimated at around 21,000 individuals, according to the zoo statement.
"Embryo transfer [into a surrogate mother] in rhinos is in its infancy and has not yet been successful in any rhino species", Dr Roth told BBC News.
Researchers also plan to extract oocytes (ovary cells) from the last two living female northern white rhinos.
In addition, researchers at the San Diego Zoo Institute for Conservation Research and the Scripps Research Institute are trying to create pluripotent stem cells using skin cells taken from a dozen northern white rhinos.More news: Tony Parker agrees to deal with Charlotte Hornets
In March, died last male Northern white rhinos Sudan. Scientists have succeeded in creating stem cells from embryos rhinoceros the southern white Rhino. These eggs were then fertilized in petri dishes with previously frozen samples of northern males' sperm.
Stejskal is part of the worldwide team of scientists and conservationists trying to keep the rhinos from slipping into extinction. "Meanwhile, we don't have enough funding to conserve the other four rhino species, all of which are more threatened with extinction than the white rhino", said Bob Smith, Director of the Durrell Institute of Conservation and Ecology at the University of Kent, England.
In the meantime, the team will practice, implanting some of their hybrid embryos into SWR surrogates "to test the system".
Northern white rhinos were once abundant across Central and East Africa, but conflicts and poaching wiped them from their natural habitat.
Scientists said the northern white could make a similar recovery through conservation efforts that make use of frozen cell lines.
An worldwide team of scientists have announced a breakthrough aimed at saving the northern white rhino from extinction.
"Rhinos are very large (2,000 kg on average), so they have a reproductive tract that is very hard to access".More news: U.S. tariffs on China take effect as Trump trade war escalates
'We are quite confident with the technology we have developed'.
The only hope for the northern white rhino is to join that list.
The northern white rhinoceros is the most endangered mammal in the world.
But genes from the northern white rhinos might live on.
The global team of researchers, led by Professor Thomas Hildebrandt from the Leibniz Institute for Zoo and Wildlife Research, have used an existing assisted reproduction technology developed for horses, and applied it to the white rhino.
Researchers have increased efforts to develop new scientific advances to bring the species back to life again. Artificial insemination - an assisted reproductive technology - has been used to produce offspring with 60 mammals, including the giant panda, black-footed ferret and Asian elephant, and 35 non-domestic birds. Now they are the only hope for the salvation of the genome of the Northern subspecies. "We should come at it with everything we've got", Roth said.More news: Keri Russell Is In Talks to Join 'Star Wars: Episode IX'!