SAN SALVADOR, El Salvador — El Salvador’s brutal street gangs have been involved in every kind of criminal activity imaginable: drugs, extortion, prostitution, murder, kidnapping.

But even authorities were surprised when a woman escaped the Mara Salvatrucha gang and told prosecutors its members had kidnapped her and forced her into a “black widow” arranged marriage. After the wedding, her new husband was killed in order to collect an insurance policy.

The gang’s hook for her prospective husband was also novel: They advertised the woman as a U.S. citizen who could get her husband a coveted entry visa to the United States.

Hers is not the only such case. Prosecutors have located and are protecting another woman who was forced into the same scheme. They say that in the two cases, in 2014 and 2016, insurance policies worth $62,000 and $30,000 were either taken out or collected. They also are investigating two suspected cases involving insurances policies of about $15,000 apiece.

Prosecutors say their efforts at determining the scope of the scam are complicated by the fact that Mara Salvatrucha may be using its own female members — who are much less likely to talk — in the frauds. Or a more sinister possibility is that the gang is killing the women as well after the policies on their slain husbands are collected.

Mara Salvatrucha is one of the three main crime organizations in El Salvador, and so far it is the only one that authorities have seen involved in the insurance scheme. The country’s insurance association said it could not discuss the cases because they are still under investigation.

The suspected crimes involve a huge amount of planning and sophistication, and illustrate the control the gangs have over some neighbourhoods, experts say.

“It was a very sophisticated, well-planned operation,” said Violeta Olivares, the head of the prosecutor’s office for human trafficking. “We have two women who were recruited under the same circumstances, and who were forced through threats, physical and psychological violence and even sexual violence, to marry two men whom they didn’t know.”

The scheme came to light when the first “bride” escaped her captors and went to prosecutors, who have granted her protection. Her name has been withheld by authorities for fear of gang reprisals.

Her nightmare began when she got what she thought was a domestic-help job from a woman called Esmeralda Aravel Flores Acosta. But when she arrived at the house she was supposed to clean, she realized it was a Mara Salvatrucha safe house.

“You are going to have to stay here whether you like it or not,” the house’s gang occupants told her, according to Olivares. “You are going to marry a stranger, and you’re going to tell him you have U.S. citizenship.”

And she did. The gang dressed her in white and took her to a town in western El Salvador, where they had her marry a man named Marvin Reyes.

Before the marriage, gang members told Reyes to take out a life insurance policy, arguing that U.S. immigration authorities wanted to see such a policy before granting him a visa, prosecutors said. The gang also probably charged Reyes for the “privilege” of marrying a U.S. citizen, but authorities don’t know how much.

Then, about a month after the wedding, the woman was informed that her husband had met a violent death. The gang ordered the “widow” to go to the morgue to claim the body and then go to the insurance office to claim the policy benefits. All the time, she was accompanied by gang members.

Eventually, the woman managed to flee the gang and contacted prosecutors, who raided the house where she had been held and found $4,000 in cash.

Police have arrested three women in the case. They are facing charges of human trafficking and conspiracy to commit homicide and fraud, and could face 20 years in prison. Other participants in the scheme are being sought.

The Associated Press was unable to contact Reyes’ family, because prosecutors declined to reveal his relatives’ names and contact information.

Activists say it is difficult to know how many women have been victims of the scam because so many women in El Salvador disappear.

“Women disappear and they are found days or months later,” says a report by the non-profit advocacy group Talk To Me About Respect. “Some have suffered abuse and extreme violence, while in other cases, only their lifeless bodies are found.”