A 43-year-old Las Vegas woman has been arrested in Mexico on charges that she lured at least four older men on dating websites, drugged them and tried to steal millions of dollars from them in a deadly scheme, the authorities said Friday.

The woman, Aurora Phelps, was charged with one count of kidnapping resulting in death in the scheme, which the F.B.I. said had led to at least three deaths.

Spencer L. Evans, the top F.B.I. agent in Las Vegas, said Friday that the investigation was “ongoing” and that Ms. Phelps might face more charges in the United States and Mexico.

In one case, Ms. Phelps drugged a man in Las Vegas after meeting him online, took him to Mexico City and used his credit card to rent a hotel room, where he died, according to a 21-count indictment unsealed this month.

Ms. Phelps pushed the man, who was “zonked out of his mind” on drugs, in a wheelchair as they crossed the U.S.-Mexico border at a pedestrian crossing, Mr. Evans said in an interview on Friday.

She took her daughter on the trip to Mexico City, in November 2022, according to the authorities. She had drugged the man during a lunch in Las Vegas one day after meeting him on an online dating service, according to the indictment, filed in federal court in Nevada.

Mr. Evans said that Ms. Phelps had stolen hundreds of thousands of dollars in a “romance scam on steroids.”

“It’s probably, in recent history, the worst one that we’ve seen,” Mr. Evans said. “But for meeting with Phelps, all of these folks would be alive.”

Ms. Phelps carried out her scheme at least from July 2021 to December 2022, taking her victims’ tech devices and bank cards, according to the indictment.

In one case, she used a victim’s bank account to buy a gold coin, days after the victim had been found dead in the bathroom of his home in Guadalajara, Mexico, court papers said.

In another case, she sold around $3.3 million in Apple stock belonging to a different victim and unsuccessfully tried to steal more than $3 million from his E-Trade account after drugging him, according to the indictment.

Court papers said that she had stolen Social Security payments and a BMW from one victim after meeting him at a Hard Rock hotel in Guadalajara.

All four of the victims mentioned in the indictment appeared to be in their 60s or 70s, and the man who survived emerged from a five-day coma after being heavily drugged, Mr. Evans said.

Ms. Phelps has been charged with one count each of kidnapping and kidnapping resulting in death, seven counts of wire fraud, three counts of mail fraud, six counts of bank fraud and three counts of identity theft.

Ms. Phelps, who remained in custody in Mexico on Friday, faces up to life in prison if she is convicted, the U.S. Attorney’s Office in Las Vegas said.

She was arrested by the Mexican authorities, the office said. The authorities declined to say when Ms. Phelps had been taken into custody.

She could not immediately be reached for comment on Friday, and it was unclear if she had a lawyer. Prosecutors wrote in court papers this month that she had been presented with an extradition warrant and that she “may challenge her extradition.”

Although the indictment described four victims, prosecutors wrote in a request to unseal the indictment, dated Feb. 10, that the “government believes that other victims exist and need to be identified.”

Ms. Phelps, a dual U.S.-Mexican citizen who was born in the United States, has lived in Nevada, Arkansas and Guadalajara, according to the F.B.I.

Mr. Evans said the F.B.I. had identified at least 10 victims, including one in Arkansas. The names of the victims have not been released.

Ms. Phelps was indicted after a two-year investigation by the F.B.I., which started with a missing-person report, Mr. Evans said.

“We’re still looking for additional evidence,” he said, adding, “I’m hoping that someone sitting back and reading the newspaper or watching TV, it might jog their memory and say, ‘Hey — that might be my uncle that disappeared, or my father, or grandfather.’”