Clay County Sheriff Rick Beseler notified the media before dawn Friday that he will announce a major development in the homicide investigation at noon.
Sources confirmed to WJXT that Harrell, named a person of interest in Somer's death when he was arrested, was charged with murder early Friday morning.
The girl disappeared in October while walking home from school in a Jacksonville suburb. Her body was found in a south Georgia landfill two days later.
Officials have not released further information regarding the announcement and Somer Thompson's family is also remaining silent for now.
MORE ON CRIMESIDER
February 12, 2010 - Somer Thompson Murder: Person of Interest Jarred Harrell Arrested with Child Porno
January 22, 2010 - Somer Thompson Murder: Mom Warned a Year Before 7-Year-Old's Abduction
November 4, 2009 - Reward Now $45K to Find Somer Thompson's Killer
October 29, 2009 - Sheriff: Help Me Catch Somer Thompson's Killer
October 27, 2009 - Somer Thompson Funeral: Little Girl Laid to Rest as Sky Fills with Purple
October 27, 2009 - More Than 1,000 Tips But No Leads in Somer Thompson Murder
October 26, 2009 - Somber Sendoff for 7-Year-Old Somer Thompson, Florida Girl Who Vanished After School
October 23, 2009 - Somer Thompson Pictures: Her Mother Vows Justice, A Community Vows Never to Forget
October 23, 2009 - In Somer Thompson Murder, Local Sex Offenders No Longer Suspects, Say Cops
October 23, 2009 - Somer Thompson's Mom to Killer: "We're Coming For You"
October 23, 2009 - How Police Found Somer Thompson and How They Hope to Catch Her Killer
October 22, 2009 - Somer Thompson Body Likely Found, Says Florida Sheriff
October 21, 2009 - Search for Missing 7-Year-Old Somer Thompson Leads to Body in Landfill
October 20, 2009 - Somer Thompson Vanished After School, Seven-Year-Old Girl Missing in Orange Park, Fla.