Image copyright Getty Images Image caption The child was found sitting in a car seat at the side of Interstate 40 in Oklahoma City (file photo)

A four-week-old was found abandoned in a car seat at the side of a major road in Oklahoma City.

Police confirmed that the child was in good condition and is believed to have been alone for just a short time.

A driver of a church youth group minibus pulled over and called emergency services after spotting the car seat at the side of Interstate 40.

The child had been left in the carrier with a birth certificate and several thousand dollars in cash, reports say.

Driver Roger Prater said he initially thought the baby was a doll, but then he saw the feet kick.

Although temperatures were as high as 33C (91F) at the time, the child seemed unaffected.

Police were able to locate the infant's mother through relatives in Texas. She was taken to a hospital for observation.

Mr Prater, a salesman, said he was still getting over the shock of what he found.

"It's something I probably won't ever see again," he said.