Elizabeth Manger was at work when her cellphone rang. The caller screamed, “We got your son, we got your son and we’re going to kill him.”

Her heart froze. Manger, a probation officer in Miami Gardens, has two sons. With the abrasive voice still screaming at her in heavily-accented English, she ran down the hall to have her supervisor call her sons. They were safe.

“They kept saying ‘how much money can you get,’ getting more tense and nasty,” Manger said. “I got so upset, I hung up the phone.”

This scam has been ringing South Florida phones for more than a year, although a recent wave has once again brought it to the attention of law enforcement.

The story is usually the same: a caller speaking Spanish or English with a Spanish accent says, “your brother was in an accident and he’s hurt, but he messed up my motorcycle and if you don’t wire money (usually around $2,000) we’re going to kill him.”

The number has a 787 area code — from Puerto Rico.

The FBI is investigating patterns of phone scams, including this story that started circulating about a year ago, said Harry Rodriguez of the FBI field office in San Juan, Puerto Rico. He said there have been some arrests but couldn’t comment on how many.

“Some of these calls have been made by inmates in the prison system in Puerto Rico,” Rodriguez said. “We’re aware of the fact that people on the outside are assisting these extortion phone calls that come from within Puerto Rico.”

Phone scams are on the rise nationwide. In 2011, the Federal Trade Commission reported more than 70,000 complaints of scams related to telephone and mobile services. There were less than 37,500 phone-related complaints registered in 2010 and less than 11,000 in 2009. These complaints do not include other kinds of scams such as fraudulent sweepstakes and prizes, debt collection or internet services.

Con artists often change their stories to target different demographics. Elderly people in every state fall victim to stories about a grandchild in trouble. For years, callers pretending to be from the Nigerian Central Bank have been going after the bank accounts of small businesses worldwide. Other fraudsters claim to be calling from power companies and credit-card companies.

Florida is the only state where people have reported receiving calls from a 787 number telling the same story Manger described. She said another Miami Gardens officer got the same call. Two Miami Herald reporters were victims as well.

When phone scams are reported to local police, they are classified as either fraud or theft, so Miami-Dade police do not have specific statistics on crimes of this type, said spokesman Javier Baez.

Although increasing awareness of the brother-in-the-motorcycle-crash story has hurt its effectiveness, there are still people who fall victim and wire money out of concern for their loved ones. Police say it’s next to impossible to recover money that is sent, usually overseas.

Describing the way scammers dial victims’ numbers, Broward Sheriff Office spokeswoman Keyla Concepcion said, “it’s hard to trace back who it is because they set it up in a way to bounce the calls.” In most cases, she added, “once the transaction is completed, the money’s gone.”