"They did save the life of that child," Greenville Police Chief Terri Wilfong said late Tuesday.
A 25-year-old married mother of a 4-year-old faces charges of giving birth in the toilet to the 6-pound boy and leaving it to die.
By calling for help, the crew got information to help get the baby warm and keep it breathing, the police chief said. Authorities declined to immediately identify the workers.
The infant was hospitalized and in good condition, Wilfong told reporters at police headquarters. The state Department of Social Services is in charge of the baby.
"We are very grateful," said prosecutor Walt Wilkins, who said he intended to "vigorously prosecute" the woman involved.
Jessica Blackham, who has no criminal record, was arrested after she came to the Greenville police station accompanied by family members, Wilfong said.
"The family is very cooperative with us," Wilfong said. "Their concern is the safety of the child."
Blackham is charged with two counts of felony child abuse and one count of unlawful neglect toward a child. If convicted on all charges, she could face up to 50 years in prison.
Authorities said she was being held without bond after being arraigned at the local jail and would be appointed an attorney. Her first court appearance was not immediately set.
Blackham came to the Bi-Lo Center Friday evening to see a circus performance with her sister, and the 4-year-old was not with them, officials said. They did not say whether Blackham's first child was a boy or girl.
Officials said they could not immediately explain what Blackham was thinking when she gave birth. Arena workers found the asphyxiating child in the cold toilet water.
Wilkins said the charges are serious because the infant was abandoned for at least 90 minutes.
"During that time a newborn needs to be in a warm atmosphere," he said.
Authorities would not discuss the identity of the infant's father.
The baby was found suffering from hypothermia, which an expert said is one of the biggest risks for babies born away from medical care. The condition could lead to infection or breathing problems if not treated quickly.
"When a baby is moist and has exposure of its skin to the air, it will lose heat very rapidly," said Dr. Christopher Robinson, a fetal and maternal medicine professor at the Medical University of South Carolina in Charleston.
Roger Newton, president and general manager of the 13-year-old Bi-Lo Center in downtown Greenville, said he'd never encountered anything like this in his 33 years of managing arenas from Ottawa, Canada, to Miami.
The manager said he'd had to deal with a death during his career, but never a birth. He said the cleaning crew members deserved high praise.
"They did everything they should have, and we're very proud of them," he said.
Rampey said the infant was admitted to Greenville Memorial Hospital in critical condition. Evidence in the women's restroom indicated the baby was born there.
Police were referring inquiries about adopting the newborn to social services, Rampey said.
Residents in this conservative region said they were shocked by the boy's discovery and concerned about both mother and child.
"It's unfortunate that anyone has to go that far, and wouldn't know what to do," said Lorna Sexton, 54, of nearby Taylors. "It broke my heart to hear it. Let's hope the girl, the woman, is able to get some help."
Associated Press writer Meg Kinnard in Columbia, S.C., contributed to this report.