JOHANNESBURG — A South African court has approved an investigation into a case of two baby girls mistakenly switched at birth in a hospital in 2010 and given to different mothers who are now in disagreement over how to resolve the traumatic situation.

The Centre for Child Law, a South African group that promotes children's rights, said Thursday that a court has appointed it to find out about the switch at a Boksburg hospital near Johannesburg, and to decide what would be in the children's best interests.

One of the mothers, who is single and unemployed, recently learned about the mistake while trying to get child support. She wants her biological daughter to be placed in her care, and to return the other girl to her biological mother, according to court documents. But the second mother has refused.

"We have to do a comprehensive investigation regarding the circumstances of the swap, the children's current circumstances and what would be in the children's best interests in the long terms," Carina du Toit, an attorney at the Centre for Child Law, wrote in an email to The Associated Press.

"The investigation will include extensive co-operation with psychologists and counselors," du Toit wrote.

The center is based in the law faculty at the University of Pretoria. On Monday, a provincial court instructed it to submit a report on the baby swap case within 90 days.

The children, now nearly four years old, were born at Tambo Memorial Hospital on Aug. 2, 2010, but the mother who wants her biological daughter back only learned about the swap recently when she and the father took paternity tests in a dispute over child support, du Toit said in an April affidavit in a provincial court.

The results concluded that neither parent was biologically related to the girl who was in the mother's care, and the father is not legally obliged to provide child support because the girl is not his daughter.

The mother approached the hospital, which acknowledged the unexplained swap and organized joint therapy sessions for the two mothers over several months ending in February. However, the mother seeking to have her biological daughter returned to her "became unhappy with the process" and took her case to children's court, according to the court documents.

In her affidavit, du Toit said she did not know the location of the biological fathers. She said each child was with a caregiver who was not recognized by the law as the child's guardian, and that litigation "might be necessary and inevitable to remedy the tragic situation in which these children and mothers find themselves."

She also said: "There is a potential conflict of interests between what the biological mothers desire as an outcome and what may be in the best interests of the children."