Spartanburg County Sheriff Chuck Wright told reporters that authorities would excavate the area after cadaver dogs signalled the possible presence of remains.

The missing woman was found inside a container measuring about 30ft by 15ft. The sheriff said she told him the bodies of other women could be buried on the land owned by Todd Christopher Kohlhepp.

Kohlhepp, a 45-year-old registered sex offender with a previous kidnapping conviction, has been arrested and charged with kidnapping.

The woman's boyfriend, 32-year-old Charles Carver, is still missing after the couple disappeared in late August.

Acting on a tip, officers found the woman after hearing her banging inside the container in Woodruff, 80 miles north west of the state capital of Columbia, the sheriff said.

The woman, who had worked for Kohlhepp, had a chain around her neck, he said. She told officers she had been kept in the container for two months and had been fed regularly.

Referring to the possibility of other victims, the sheriff said: "We're trying to make sure that we don't have a serial killer on our hands."

Anderson Police Chief Jim Stewart said his department's investigation into the couple's disappearance led authorities to the property near Woodruff.

"We got computer and cellphone records that ultimately led us to the area in Woodruff. We knew that was the last place that a cellphone tied to this case pinged."

Records indicate Kohlhepp is a licensed estate agent and a licensed pilot. In 1986, he was convicted and sentenced to prison for kidnapping and crimes against children.