MEMPHIS, Tenn. - Four young children in suburban Memphis were fatally stabbed Friday and their mother was taken into custody, authorities said.

Deputies were called to an apartment complex in the county shortly before 1 p.m. Friday, said Shelby County Sheriff Bill Oldham, who did not specifically allege that the mother had stabbed the children.

"This is an egregious act of evil that has shocked us to our core," Oldham said. "I will never understand how anyone can do this."

Officials have not released the ages of the children, but sheriff's office spokesman Earle Farrell said deputies responding to the scene called them "babies."

The investigation is in a very preliminary stage and investigators do not know if the mother had any mental health issues, Oldham said. He said authorities are working to notify the next of kin and won't release names before that.

"One of the most difficult questions in any investigation is always, 'Why did this happen?'" he said.

The apartment where the stabbing occurred is in a gated community with a golf course called The Greens at Irene.

On Friday afternoon, deputies were standing at the gate house questioning motorists as they tried to drive into the neighbourhood.

Neighbour Patricia Johnson spoke with reporters from her car as she drove out of the neighbourhood Friday afternoon. She said she wasn't allowed to leave for two hours as deputies investigated the scene. She has a child, and said she burst into tears when she heard about the killings.

"I can't fathom that," she said. "What would babies do to make you do that?" Oldham said the district attorney general's special victims' unit has been called in and Shelby County Mayor Mark Luttrell has promised all resources necessary for the investigation.