SANTO DOMINGO, Dominican Republic -- The shadowy tipster who made explosive allegations involving U.S. Sen. Bob Menendez and underage prostitutes in the Dominican Republic named names. He gave descriptions of the women, and in some cases, phone numbers and addresses.

Despite those details, the women are nowhere to be found.

A week after the claims made headlines in the United States and on this Caribbean island, the alleged prostitutes have disappeared. An attorney who once represented two of the women said he hadn’t spoken to them in months, and then stopped returning phone calls himself. A two-bedroom apartment where some of the alleged liaisons took place is now vacant. Little remains here beyond hazy memories.

No concrete links have been made between Menendez and any prostitutes. Still, the allegations from the tipster, who identified himself as Peter Williams, were serious enough to launch an FBI probe. And shreds of evidence in Santo Domingo show that, at the very least, the women Williams described exist.

Take an apartment in Santo Domingo’s upscale Gazcue neighborhood that Williams said was used for sexual liaisons. In April emails to a watchdog group, Citizens for Responsibility and Ethics in Washington, Williams alleged that Dr. Salomon Melgen, a friend and major campaign donor to Menendez, rented a unit for a Brazilian prostitute named Maria and a Colombian prostitute named Geraldine.

The apartment exists. When reached by phone, the landlady said that two young women named Geraldine and Maria had indeed lived there last year, and said the nationalities matched.

However, the landlady, who declined to be named, did not believe the women to be prostitutes — she said she thought they were beautiful foreign exchange students — and had never heard of Menendez or Melgen visiting the apartment. But she complained that the women had nearly destroyed the unit, even leaving the wallpaper torn up when they abandoned the apartment last year.

“They behaved very badly,” she said. The apartment has since been rented to others and is now back on the market for $1,000 a month.

The FBI is investigating the sex allegations, some of which involve minors.

Prostitution is not illegal in the Dominican Republic. The investigation is also probing trips Menendez took on the eye doctor’s private plane, and the senator’s gift disclosures. Last week, Menendez acknowledged that he had traveled to the Dominican Republic with the doctor on three occasions, and cut a check for more than $58,000 to reimburse him for two of the flights.

Separately, the agency is investigating Melgen in connection with possible Medicare fraud. Last week, FBI agents raided Melgen’s eye clinic in West Palm Beach.

Representatives for both Menendez and Melgen have denied wrongdoing.

The emails from Williams to the authorities were met with some skepticism, in part because he was unwilling to meet with investigators or talk over the phone. “Williams” — which is likely a pseudonym — said he wouldn’t speak because he was concerned with the women’s safety and did not want to become a celebrity accuser.

But there were many facts the tipster got right. He knew the addresses of Melgen’s homes in Santo Domingo and the exclusive Casa de Campo resort, where the parties allegedly took place, and the names of his bodyguards and other employees.