COLUMBIA - A Myrtle Beach couple has been charged with murder and kidnapping in the case of a missing 20-year-old woman whose body has not been found, authorities said Monday.

During a news conference, Horry County Police Chief Saundra Rhodes said Tammy Moorer, 41, and her 38-year-old husband Sidney face those charges in the death of Heather Elvis.

Elvis' family says she was last heard from around 3 a.m. on Dec. 18, after she went on a date. Her cellphone gave out its last signal around that time and her car was found abandoned at a boat landing Dec. 19.

The Moorers were initially arrested Friday and charged with indecent exposure and obstruction of justice in the case, but authorities released no other details about the charges or the investigation that led to them. On Monday, Rhodes also declined to release much information, saying only that that additional evidence found at their home led investigators to bring the kidnapping and murder charges against the couple.

"We were searching the property for any evidence that would lead us to probable cause in this case, a body included," Rhodes said. "Obviously the investigation is still ongoing. The evidence that we located there led to the charge of murder."

Attorneys said to be representing the couple did not immediately return messages Monday. Rhodes said they would be in court next during the week of March 17.

Police and volunteers on foot, all-terrain vehicles and horseback have repeatedly organized searches for the woman, but have found no trace. Her family created a Facebook page to ask for help to find Elvis, offering a $30,000 reward for information that brings her home. Several companies have donated billboard advertising to put up pictures and information on Elvis.

Two other men have been charged with obstructing justice in the case by posting misleading information about it on Facebook. Deputies said in January that those posts created a community reaction that diverted officers investigating Elvis' disappearance.

Elvis is just one of nearly a half-dozen young people who vanished with barely a trace around Myrtle Beach in the past few years. Several have been found. Others, like New York state native Brittanee Drexel - who was 17 when she disappeared during a spring break trip to Myrtle Beach in 2009 - are still unaccounted for.