Last Updated at 1:02 p.m. EDT
Investigators found the safe stolen from a Florida couple's home during a deadly break-in last week, officials said.
State Attorney Bill Eddins said Thursday that investigators have also found several guns and believe at least one of them was used to kill Melanie and Byrd Billings.
The couple was known for adopting children with special needs. Surveillance cameras captured footage of masked men - some dressed as ninjas - slipping into front and back doors of their home.
Eight people have been charged - seven with murder and one with being an accessory after the fact.
Eddins would not say what was in the safe or where it or the guns were found. He said the case is mostly wrapped up. But Sheriff David Morgan said investigators are still looking for people they want to interview.
Morgan also confirmed that the Drug Enforcement Administration is taking part in the investigation into the Billings' deaths - a development which may indicate the federal agency's interest in possible drugs and money laundering, reports CBS News correspondent Terrell Brown
Morgan said he called in the DEA after information surfaced during the investigation that fell into the scope of the agency's authority, but declined to reveal the specific evidence.
A clearer picture of the Billings' finances emerged earlier Thursday revealing the murdered couple.
Meanwhile, authorities continued investigating the precisely executed, deadly break-in at the victims' Florida Panhandle home, with the Drug Enforcement Administration confirming their involvement in the case and police arresting an eighth suspect. Police are also still seeking at least one more accomplice who they believe failed his assignment to disable the house's surveillance system.
Court documents show the Billings, who were known for adopting 13 children with special needs, sued their own adult son for child support in 2008 after they took in his daughter - their granddaughter - in 2006, reports CBS News correspondent Terrell Brown.
They also had asked for a $50,000 life insurance policy for the then-18-year-old girl, with themselves as the beneficiaries.
Morgan told CBS' "The Early Show" that the police have not investigated the Billings' finances as they've searched for their killers.
Other federal agencies are also involved in the case. The Bureau of Alcohol, Tobacco and Firearms is helping trace the weapons used in the attack and the FBI is working to enhance the security video retrieved from the house.
Footage taken by the cameras helped lead investigators to the suspects in last week's shooting deaths. The videos showed masked men - some dressed as ninjas - slipping into front and back doors at the home.
Police on Wednesday arrested an eighth suspect, 47-year-old Pamela Long Wiggins, charging her with accessory after the fact to felony murder, Morgan said. Seven others have also been charged in the killings.
Police do not believe Long, the eighth arrest, was present at the murder scene but do suspect she may have personal ties to the alleged mastermind of the attack - Leonard Patrick Gonzalez Junior, reports Brown.
CBS News obtained a marriage license from December listing Long as the bride, with Gonzalez as a witness.
Morgan said the suspects spent 30 days training for what was a precisely executed break-in, save for the failure to turn off the couple's camera system. Before the crime, the extensive surveillance system was used to monitor the children.
"The execution was basically flawless," Morgan said. "The one gaping hole that would not have made this a perfect operation, if you will, was the fact that the surveillance system was not disabled. I guess the question was why was it not?"
Morgan said an accomplice was assigned to turn off the cameras, possibly remotely, but never did - and the men who broke in apparently didn't know that. Morgan said authorities are looking for another person of interest who may have been the one assigned to turn off the system, though he did not identify that person.
The surveillance videos led investigators to a red van used as a used as a getaway car and eventually to the suspects, a loosely connected group of mostly day laborers who knew each other through a power washing business and an auto detailing operation.
They were in the nine-bedroom house for just four minutes and on the property for 10, Morgan said.
Morgan said the suspects took a safe from the house, though he would not say what was in it or what else was taken. Authorities have said the main motive was robbery, though there may have been others.
He said earlier that Wiggins is a friend and landlord to the 35-year-old Gonzalez Jr., whom Morgan described as a "pivotal person" in organizing the break-in. Gonzalez, who's charged with murder, proclaimed his innocence in court Tuesday.
The male suspects range in age from 16 to 56.
Nine of the couple's 13 adopted children were home during the break-in. Three saw the intruders but were not hurt. The couple also had four children from previous marriages.