Two suspects were charged in a case that spans four states and highlights vulnerabilities in a federal visa program for immigrants. On first glance, a slew of eight armed robberies at mini-marts and liquor stores in four states this year appeared to be run-of-the-mill crimes. But F.B.I. agents investigating them noticed patterns that they said could suggest a more complex operation: The robberies, including at least one that involved an apparently fake gun, were staged as part of an elaborate visa-fraud scheme.

According to the New York Times, after a nearly a decade of delays, federal officials began allowing U visa applications en masse as defense lawyers began to raise alarms about fraud. One public defender from Marin County said that U visas could create “irresistible incentives for people to invent or exaggerate offenses.”

As reported by the New York Times, six women were accused of posing as victims of domestic violence to secure U visas and to gain subsidized housing. The reporter noted that 36,000 people had sought help at city centers since 2005 and no documentation was required to prove abuse.