SAN SALVADOR, El Salvador (AP) — Journalists from an investigative news outlet in El Salvador sued NSO Group in United States federal court Wednesday after the Israeli firm’s powerful Pegasus spyware was detected on their iPhones.

In January, the University of Toronto’s Citizen Lab, an internet watchdog, reported that dozens of journalists and human rights defenders in El Salvador had their cellphones repeatedly hacked with the spyware.

Among them were journalists at the El Faro news site.

“These spyware attacks were an attempt to silence our sources and deter us from doing journalism,” Carlos Dada, El Faro’s co-founder and director, said in a statement released by the Knight First Amendment Institute at Columbia University, which filed the lawsuit on behalf of the El Faro journalists.

“We are filing this lawsuit to defend our right to investigate and report, and to protect journalists around the world in their pursuit of the truth,” Dada said

NSO Group did not immediately respond to a request for comment about the lawsuit.

NSO, which was blacklisted by the U.S. government last year, says it sells its spyware only to legitimate government law enforcement and intelligence agencies vetted by Israel’s Defense Ministry for use against terrorists and criminals.

In response to the Citizen Lab report in January, NSO said it does not operate the technology once it is given to a client and cannot know the targets of its customers. But it said the use of its tools to monitor activists, dissidents or journalists “is a severe misuse of any technology and goes against the desired use of such critical tools.”

It said it has terminated multiple contracts in the past due to client misuse.

At the time, a spokeswoman for the administration of Salvadoran President Nayib Bukele said the government was not a client of NSO Group and had no association with Pegasus.

Carrie DeCell, senior staff attorney with the Knight First Amendment Institute, said, “The use of spyware to surveil and intimidate journalists poses a truly urgent threat to press freedom.”

The lawsuit alleges NSO Group violated U.S. law by developing spyware and deploying it against the El Faro journalists.

Apple and WhatsApp have pending lawsuits against NSO Group in the same U.S. court in the Northern District of California.