The two anonymous callers told police about two men who could have killed three members of an Ohio farm family on Tampa Bay two years ago. Then they hung up.
Detectives on Tuesday publicly appealed to those callers, including one who identified the suspects by name, to contact them again with more information.
As an extra incentive, police are raising a $5,000 reward to $25,000.
"The (callers) know what they're talking about," said St. Petersburg detective Sgt. Glen "Boomer" Moore, who is heading the investigation of the 2-year-old murders of Joan Rogers and her two teen-age daughters.
"We've been able to verify a lot of the information and we feel very good about this information. In order for us to go further in this investigation, we need to talk to these callers again.
"This is by far the best thing we've had yet," he said.
The bodies of Joan Rogers and her daughters Christe, 14, and Michelle, 17, rose to the surface of Tampa Bay two years ago Tuesday.
The murders, which have remained unsolved despite 1,700 tips and 20,000 hours of investigation, have been called the most heinous in the history of the Tampa Bay area.
Some relatives of the Rogers family marked the anniversary Tuesday by putting up ribbons near their Willshire, Ohio, dairy farm.
"I'm happy that they've got something there," said father and husband Hal Rogers, referring to the police statements.
Equipped with a new FBI psychological profile of the killer, police announced two weeks ago they believe a controlled, meticulously neat, serial killer enticed the Rogers women aboard a boat June 1, 1989, after the family checked into the Days Inn on Rocky Point in Tampa.
The killer, who probably had a helper, raped them, weighted and bound them and tossed them alive into Tampa Bay. The killer would have had access to a blue and white boat and probably was experienced in boating on Tampa Bay.
The new information produced 200 leads, including 50 considered worthwhile by detectives. Moore said police now have seven potential suspects.
At the top of the list are a pair of men who were described by two anonymous callers on May 21, the day after police made their plea.
"One of the callers was very specific about the information," Moore said. "We have done extensive checking into that and we feel very good about it."
Police are hoping the $25,000 reward, believed to be the largest the Police Department has ever offered, will bring information leading to an arrest.
Moore also repeated a warning that anyone who knows who the killer is will be in danger because of that knowledge.
Moore also appealed Tuesday to the public for more information.
"We believe that the suspect is an established person in the community, has a good job, is grounded in this community," Moore said. He may be "somebody they may never suspect, a relative, a husband, maybe a boyfriend."
The FBI profile describes the killer as a confident, controlled man who is compulsive in his behavior.
The man is intelligent and very interested in the Rogers case. He indulges in sexual fantasies, possibly involving bondage. He is white and between 25 and 40, police believe.
Police say he, or his helper, would have been able to navigate in the dark from a public boat ramp on the Tampa side of the Courtney Campbell Parkway, where the boat left shore, to a spot 18 miles south where the women were thrown overboard.
The killer also would have owned or had access to a 20- to 25-foot blue and white boat in June 1989. The boat, which would have been neat and clean, may have been sold since then.
Anyone with information about the case can contact police anonymously by calling 893-7104.