It's been a week since Gavin Smith, a 57-year-old 20th Century Fox executive, went missing, and his son said he left few clues to solve his disappearance, as a Twitter and Internet campaign gains steam to find him.

Smith's son, Evan Smith, a forward on the University of Southern California's basketball team, said on Twitter that he's not giving up in the search to find Gavin Smith.

I will not stop until I find my father, the younger Smith tweeted Sunday. A son never gives up on his father.

Smith's Twitter feed is filled with optimistic and sympathetic users, who are praying Gavin Smith will be found safe.

WOW. So many people have come to my family's side in these times of despair and confusion. i thank each and everyone of you for your support, Evan Smith tweeted Monday.

Evan Smith told Reuters Monday that his father, a film distribution executive for 20th Century Fox, has not used his cell phone or credit cards since his disappearance, which makes it difficult for authorities to piece together where Gavin Smith might be. Pinging the cell phone has not worked and it is presumed that the device is turned off.

We're just doing our best to get as many people looking as possible, Evan Smith said. We're trying to find my dad. We need our father.

Gavin Smith was last seen at his home in Oak Park, Calif., near Los Angeles, between 9 p.m. and 10 p.m. May 1, according to findgavinsmith.com, a site created to track the latest developments and encourage anyone with knowledge of Smith's disappearance to come forward.

The site also is helping coordinate search parties to find Gavin Smith.

Smith left the home in his black 2000 Mercedes 420E class car, which has padded storage racks and tinted windows.

Gavin Smith, 57, is described as 6 feet, 6 inches tall, 210 pounds, with grey hair with blonde highlights and green eyes. He also has a goatee, a 5-inch scar on his calf and a 4-inch scar on his inner right wrist.

He was last seen wearing purple pants and black and gray shoes.

Evan Smith told Reuters his family became concerned when his father failed to show up for work since Gavin Smith loved his job.

My dad's a good guy, a very responsible man, and it all really took hold for us when he didn't show up for work, he said.

Evan Smith's sister, Tara Addeo, said Gavin Smith would never abandon his family.

My biggest concern is that he did not pick up his son, which he was supposed to pick up on Wednesday morning to take him to school, and that is a concern for me, she told KABC TV in Los Angeles.

20th Century Fox, is equally concerned over the distribution executive's disappearance.

We are extremely worried about our friend and colleague Gavin Smith and are actively doing what we can to assist the Los Angeles Sheriff's Department in their search for him, Chris Aronson, vice president of domestic distribution for Fox, said in a statement, Reuters reported.

If you have any information on Smith's disappearance, contact Det. Abraham or Det. Carns at the Los Angeles County Sheriff Department's Homicide Bureau at 323-890-5500 and refer to file number 012-02470-2254-400.

You can also submit tips online by visiting http://lacrimestoppers.org, phoning tips to 800-222-TIPS or via texting by texting TIPLA plus your tip to 274637 (CRIMES.)

In addition, information can be submitted to findgavinsmith@gmail.com.