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(CNN) -- For 19 years, the cold case of two slain prostitutes weighed heavily on the small military town of Oak Grove, Kentucky, especially after the brothel's madam publicly accused two allegedly corrupt police officers of the killings.

Because the madam's accusation was boldly made during a City Council meeting three years after the deaths, everyone in town has long known of the suspicions, but local police and the Christian County Sheriff's Office were unable to crack the case.

Now, a seven-year investigation by the Kentucky State Police has resulted in charges against the two police officers, both of whom have since left the force, and a third man. One of the former officers was a detective who appeared at the crime scene with other officers to investigate the killings, said one former officer who was first on the scene.

For now, Oak Grove, adjacent to the U.S. Army's Fort Campbell, is feeling relief from the tantalizing mystery, but the town's mayor said Wednesday he suspects the case could become even bigger.

"I think this is just the tip of the iceberg. I think there are more arrests coming," said Dan Potter, who wasn't mayor when the killings occurred in 1994. "Wouldn't the other police officers know?"

One of the former officers, Leslie Duncan, 50, already is serving a three-year prison sentence after pleading guilty in September to tampering with physical evidence in the case, state police said.

Duncan, of Central City, Kentucky, was charged this month with two counts of complicity to murder, police said.

Duncan's defense attorney did not respond to CNN's requests for comment.

Former officer Edward T. Carter, 43, of Somerset, Kentucky, was charged with two counts of murder and is being held by the Warren County, Ohio, Sheriff's Office pending his extradition to Kentucky, said Kentucky State Trooper Stuart Recke said. It was not immediately clear if Carter has retained an attorney.

A third man who was never a police officer, Frank J. Black Jr., 39, of Gadsden, Alabama, also was charged with two counts of murder and is being held by Alabama authorities pending extradition to Kentucky, Recke said.

Black's father, Frank Sr., told CNN that his son -- who was living in nearby Clarksville, Tennessee, at the time of the killings -- is innocent and says he isn't sure how his son came to be associated with Duncan and Clark -- or if they were at all.

Carter and Black are being held in lieu of $1 million bail, Recke said.

The charges against all three men stem from the 1994 killings of Candace Belt, 22, and Gloria Ross, 18, who worked as prostitutes at the New Life Massage Parlor, police said.

"Needless to say, since it's an open and active investigation, we can't get too much into the details," Recke said this week. "The Kentucky State Police got the investigation back in 2006. Our investigators, once we get an investigation from another agency, we start from square one and go through all the information available with a fine-tooth comb."

A fellow officer's suspicions

Former officer Bob Combs, who was first to arrive at the scene of the killings, recalled his suspicions of Carter and Duncan at the time.

"I suspected that they may have been involved, but didn't have evidence," said Combs, who had joined the force only a year before.

Belt, a mother of two, "was still alive" when he arrived, Combs said, "but she died on the way to the hospital."

"Once Duncan got there, he was the detective, so it became his scene," he said.

In an interview this week with CNN, Combs claimed Duncan disturbed crime scene evidence.

"Duncan ran in there and messed up the scene. The phone was off the hook when I arrived, but then after Duncan was in there, the phone was back on the receiver," Combs said. "No one had ever asked me -- the first officer on the scene -- anything about this case. No one ever asked me anything until the state police took over -- years after it happened."

Combs, who went on to be a city councilman and served until last year, said he and Duncan had been friendly back then.

"He could be a nice guy, but he could have a real temper," Combs said.

Ex-madam: 'They knew we had stuff on them'

Three years after the killings, then-Councilwoman Patty Balew announced that she, too, was a former prostitute at the massage parlor. She and other prostitutes gave police sexual favors at a discount or at no cost, she alleged.

"If they were police officers, that's what we had to do whether we wanted to or not, which we didn't like," Balew told CNN in 1997.

This week, Combs recalled the city council meeting in 1997 when Tammy Papler, the massage parlor's madam, dramatically accused the police officers of extortion and murder.

Papler couldn't be reached by CNN for comment this week. But in a 1997 interview, Papler alleged of police: "They weren't getting any more money from us, and they knew we had stuff on them. The only way to keep us quiet is to kill the girls and put us in jail."

Papler made further accusations in the CNN article that year, when she had already quit being a madam.

"I did what they told me to do," she said. "If they needed new police lights, I bought new police lights. If they needed birthday money, I gave them birthday money. If they needed money for a trailer to be moved ... basically anything they told me they needed, I gave them the money for it."

Belt and Ross were shot in the head, and their throats were slashed, Papler said.

"It was devastating to us," Papler said in 1997. "They both had babies. One was breastfeeding her baby. It was just a few weeks old."

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A pall in the aftermath

Also in 1997, the Christian County sheriff's department said crime scene evidence was botched by police, and then-Sheriff Thomas Scillian said Carter was a prime suspect. He had been at the scene 30 minutes before the slayings, according to authorities.

"There's other information that we have that leads us to believe that Carter would be a good suspect," Scillian said.

Then-Mayor Bobby Mace said the killings cast a pall over the small town: "There's a cloud hanging over us right now and there's no rain," he said. "Let's get it to either rain or let the wind blow the cloud out and let's get moving forward to the future."

In 1998, a federal court in Kentucky ruled in favor of Ross' husband and her two children in their lawsuit against Tammy and Ronnie Papler, who owned the massage parlor business, court papers show. The court issued a default judgment against the Paplers for failing to respond to, or defend against, the Ross family's lawsuit, which accused the Paplers of negligence in Ross' death.

A U.S. District Court judge, however, dismissed the Rosses' negligence claims against Louise Seawright, the owner of the building where the massage parlor was located.

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CNN's AnneClaire Stapleton contributed to this report.