(Reuters) - A Tennessee woman was charged on Saturday in the stabbing deaths of her four children under the age of five, the Shelby County sheriff said.

Shanynthia Gardner, 29, was charged with multiple counts of first-degree murder and Sheriff Bill Oldham said at a news conference that additional charges could be filed.

The children, aged 4, 3 and 2 years old, and 6 months old, were found shortly after noon on Friday in an apartment in southeast Shelby County, just outside Memphis. A fifth child, a 7-year-old boy who was also Gardner's son, escaped uninjured, Oldham said.

Shelby County Sheriff's Office Public Information Officer Earle Farrell said by telephone that the 7-year-old was in the custody of relatives.

Gardner will probably not be arraigned before a judge until Tuesday, Farrell said, due to the July 4th holiday on Monday.

The children's aunt works for the sheriff's office, Oldham said, bringing the tragedy especially close to home.

"It's a tragic scene and it has shocked us to our core," Oldham said at an earlier news conference on Friday. He said the deaths were an "egregious act of evil and a tremendous loss."

(Reporting by Fiona Ortiz in Chicago; Editing by Greg Mahlich and James Dalgleish)