PHOENIX — Thirty men called two officers posing as 16-year-old girls, showed up at a Tempe hotel and attempted to pay for sex, according to investigators, but dozens more were scared off by the prospect of committing a felony during a two-week operation targeting men soliciting underage prostitutes.

The 30 suspects who completed the transaction were arrested on felony allegations, but the 25 men who hung up when they learned of the girls’ supposed ages committed no crime and were not arrested. The interactions of all the men, and one woman, who called the undercover officers were captured on tape, and this week the Maricopa County Sheriff’s Office released tapes of those who were not charged because the evidence is not being used in a criminal prosecution.

The calls illustrate the explicit conversations the undercover officers had with the men, which prosecutors require in some detail in order to bring solicitation charges, and the responses from the men, including some who began to lecture the supposed teens.

None of the men committed any crime by phoning the women, and none was arrested, the Sheriff’s Office said.

The cases against the solicitation suspects have begun making their way through the court system, where the recent focus on the sex trafficking of minors, which has seen a host of politicians, including Gov. Jan Brewer and Phoenix Mayor Greg Stanton, take a stand against the crimes, could run up against the quest for efficient justice.

The suspects arrested in the sheriff’s operation could face years in prison if convicted of the Class 2 felony of child prostitution, but such cases are frequently challenged by defense attorneys and pleaded down to lesser charges by prosecutors.

County Attorney Bill Montgomery, who served on Brewer’s human-trafficking task force that recommended tougher penalties for defendants who solicit sex from minors, declined to comment on the sheriff’s sting because the cases are still being prosecuted.

The sheriff’s operation was not limited to targeting child predators: Investigators made 21 arrests on drug-related charges and recovered 32 pounds of methamphetamine, nearly 500 pounds of marijuana and about $35,000 during the 12-day detail.

Sheriff’s detectives also made 18 arrests at adult businesses in the area for unlicensed employees, the Sheriff’s Office said.

But it was the volume of calls that the undercover detectives received and the number of men who went ahead with their intentions after learning the girls’ supposed ages that took some investigators by surprise.

“It was how compulsive these guys were, the predatory side of these guys,” said Capt. Steve Bailey. “They couldn’t help themselves.”