The FBI has joined local authorities and the Mississippi Highway Patrol in investigating the disappearance of a family of three from their home in rural Yazoo County.

Michael and Rebecca Hargon (search) and their 4-year-old son, Patrick, have been missing since Saturday.

Yazoo County Sheriff James Williams said Wednesday night that local investigators requested the FBI's assistance.

"Anything we need, they're going to help us with the investigation," he said.

Investigators found dried blood droplets, shell casings and what appears to be bullet holes in the walls inside the home.

However, there was no sign of forced entry and the family's three cars were still at the home.

There were no signs of robbery, authorities said. Rebecca Hargon's wedding and engagement rings and the family's guns were still in the house.

Samples of the blood found inside and outside the house are being tested by the Mississippi state crime lab. Investigators hope to determine if the blood belongs to one of the family members. Williams was not sure when the results of those tests would be available.

A pickup truck belonging to the Hargons was also taken by investigators.

The parents of Rebecca Hargon, 29, a physical therapist, and Michael Hargon, 27, a construction worker, appeared on a national television news show on Wednesday morning, hoping to draw attention to their case.

In April 1994, Michael Hargon's father, Haywood, was murdered on the same property. The property was the site of a convenience store then.

Relatives have put up a $25,000 reward for the safe return of the Hargons.

Also, Mississippi Crime Stoppers (search) is offering a $1,000 reward for any information that leads to the Hargons being found.

"We are getting a lot of phone calls from different places, but so far they haven't consisted of anything," Williams said.

Rebecca Hargon was born and raised in Missouri.

He parents, Bill and Linda Hirtz, of Poplar Bluff, Mo., have been in Yazoo County (search) since Saturday.

Rebecca's aunt, Trudy Duncan, of Poplar Bluff, said efforts have begun in Missouri to help find the missing family.

"Everyone's just so helpless, and there's nothing we can do," she said. "Please pray. Keep those prayers coming."