Girl, 4, and her brother, 2, are swept to their deaths during picnic outing to a creek in California's Mountains with their mom

Two young children have died after getting caught up in the rough waters of a California stream on an excursion with their mother.

A four-year-old girl and her two-year-old brother entered the fast-moving water of a creek in San Bernardino on Tuesday. 

The kids were playing near Mill Creek while on a day out to the Thurman Flats Picnic Area with their mother. 

While the mom was tending to her son, the girl entered the water and got swept down the stream, according to the San Bernardino County Sheriff's Department.

The mother began a desperate search for her daughter - but when she returned to the little boy, she realized he had also disappeared. 

Two young children have died after getting caught up in the rough waters of a California stream on an excursion with their mother

A four-year-old girl and her two-year-old brother entered the fast-moving water of a creek in San Bernardino on Tuesday

The little kids were playing near Mill Creek while on a day out to the Thurman Flats Picnic Area with their mother

'After frantically searching, she hiked up to the picnic area and contacted another family to help search for the children but were unsuccessful in locating them,' said the sheriff's statement.

Fire and law enforcement officials were enlisted to help in the desperate search for the young kids. 

The little girl was finally found at 4:39pm and her brother at 5:04pm near the creek's edge, abc7 reported.

A San Bernardino County Fire swift-water rescue team ultimately managed to locate them in the water. 

The girl was sent to Redlands Community Hospital by ambulance while the boy was airlifted to Loma Linda University Medical Center. 

The mother frantically began to search for her daughter - but when she returned to the little boy, she realized he had also disappeared

Fire and law enforcement officials were enlisted to help in the desperate search for the young kids

Despite being rushed to local hospitals and receiving life-saving measures, both of the children were tragically pronounced dead at the hospital, the sheriff's statement said

The heartbreaking incident remains under investigation and the children are yet to be identified

Despite being rushed to local hospitals and receiving life-saving measures, both of the children were tragically pronounced dead at the hospital, the sheriff's statement said. 

The heartbreaking incident remains under investigation and the children are yet to be identified. 

Mill Creek is a 17.8-mile-long stream located in the San Bernardino Mountains.