(CNN) -- A 25-year-old woman has been charged with first-degree murder in the California death of a deployed Marine's wife, San Diego County authorities said Friday.
Jessica Lynn Lopez, 25, was being held Friday after she pleaded not guilty at her arraignment a day earlier and her bail was set at $3 million, said Steve Walker, a spokesman for the San Diego County district attorney.
The investigation into the death of Brittany Killgore, 22, is ongoing and additional charges could be filed, Walker told CNN Friday.
Marine Staff Sgt. Luis Ray Perez, 45, who was on a date with Killgore when she was last seen alive a week ago, was charged earlier this week with two felonies unrelated to Killgore's death -- receiving stolen property and possession of an assault weapon -- and he has pleaded not guilty, authorities said.
If convicted, Lopez would face 25 years to life in prison; Perez would face up to three years if convicted, Walker said.
The San Diego County Sheriff's Department said this week that Perez was being "actively investigated" in connection with Killgore's death. "We believe he knows more than what he initially told us," said Sheriff's Capt. Duncan Fraser. "We do not believe he is being cooperative with us."
Killgore, 22, was seen last Friday night when she left her apartment wearing an evening dress, heading out on the date with Perez, who is based at Camp Pendleton in San Diego County, investigators said.
Perez was questioned after a friend filed a missing person report for Killgore and he was later arrested on charges of possession of a stolen assault rifle, authorities said.
Investigators later found Killgore's body in a rural part of neighboring Riverside County. Authorities have not said how she died.
Lopez's relationship to Killgore has been unclear. CNN affiliate KGTV in San Diego reported that authorities found Killgore's body based on leads stemming from Lopez's arrest.
Lopez was found at a Ramada motel near the San Diego airport Tuesday after paramedics responded to a call for medical help. She was briefly hospitalized with lacerations and then jailed on suspicion of involvement in Killgore's death.
Killgore had recently filed for divorce from her husband, Marine Lance Cpl. Cory Killgore, who was serving with an artillery unit in Afghanistan's Helmand Province, investigators said. He was granted an emergency leave to return to the United States when he learned his wife was missing.
San Diego County District Attorney Bonnie M. Dumanis issued a statement saying: "This is an ongoing investigation and, as the county's top prosecutor, my responsibility is to protect the integrity of the case, ensure a thorough investigation, and ultimately hold those responsible in a court of law."