The Sudanese woman freed from death row has reportedly been detained at Khartoum airport as her family tried to fly out of the country.
The lawyer for Meriam Ibrahim said she, her husband and two children were detained at the airport as they tried to board a flight and were being questioned over their travel documents.
Meriam Ibrahim was freed on Monday by an appeals court in Sudan, which cancelled the death sentence imposed on her.
In a case which sparked international outrage she had earlier been sentenced to death for being married to a Christian and renouncing Islam. She gave birth while she was imprisoned to her second child.
Mrs Ibrahim's husband Daniel Wani is a Christian from south Sudan and is a United States citizen.
The BBC reports that the US was working with Sudan to ensure the family can leave the country.
US State Department spokeswoman Marie Harf said Sudan's government had given assurances that Mrs Ibrahim and her family were safe.
Earlier, a top Sudanese official told the BBC that although Mrs Ibrahim is Sudanese, she was using emergency South Sudanese papers with a US visa.