Puerto Rico's lead federal prosecutor, Rosa Emilia Rodríguez, announced Tuesday that three people have been arrested as part of a federal probe into an alleged fraud scheme involving former FEMA officials and hurricane relief funds.

"At the cost of our suffering ... they took advantage of the most vulnerable moments the people of Puerto Rico were living through to enrich themselves," Rodríguez said at a news conference in Spanish.

The three people are Ahsha Tribble, who was a FEMA deputy regional administrator and is now on unpaid leave from the agency, former FEMA staff assistant Jovanda Patterson and Donald Keith Ellison, former president of COBRA Acquisition, an Oklahoma-based energy company operating in Puerto Rico as the main contractor for the island's power authority as it sought to restore and rebuild the electrical grid destroyed by Hurricane Maria in 2017.

They face 15 counts including wire and disaster fraud as well as conspiracy to commit fraud.

Tribble, Patterson and Ellison had come to Puerto Rico in October 2017 as part of the federal government's hurricane recovery efforts, specifically to restore the U.S. territory’s electric power grid. Its destruction had caused the world's second longest blackout.

According to the indictment filed last week, both Tribble and Patterson received gifts such as hotel stays, access to credit cards and an apartment in New York in exchange for helping Ellison and COBRA Acquisition land hurricane recovery contracts in Puerto Rico.

The Department of Justice said in a statement the indictment against the defendants alleges they used Tribble’s positions in FEMA to "defraud the United States."

COBRA Acquisition obtained two contracts worth over $1.8 billion combined while Tribble was overseeing FEMA's work and Ellison was COBRA's president.

It's not clear how much of that total the energy services company billed to the Puerto Rico power authority or how much hurricane relief funds might have been used. However, the work performed under both COBRA contracts was expected to be paid through the Puerto Rico power authority with federal funds from FEMA.

The Department of Homeland Security's Office of the Inspector General, with the support of the Federal Bureau of Investigation, conducted the arrests Tuesday morning: Tribble in Florida, Ellison in Oklahoma and Patterson in California, Rodríguez said. They will be brought to Puerto Rico to face the charges in court.

"Corruption in DHS and FEMA will not be tolerated," James Long of the Department of Homeland Security said Tuesday.

Puerto Rico Governor Wanda Vázquez echoed Long's words in a statement written in Spanish saying that her administration "reproaches corruption, wherever it comes from."

"That is why we work daily to come up with stronger ways to identify possible behaviors from anyone who intends to take advantage of the need and pain of our people," she added.

Rodríguez described an instance in which Tribble allegedly pressured senior executives at the Puerto Rico power authority to use COBRA employees, instead of the authority's employees, to fix an electrical substation in San Juan that had exploded in Feb. 2018.

“While there is no known cure to permanently rid society of corruption, there are certain powerful antidotes, namely, arrests and prosecutions," Douglas A. Leff of the FBI said in a statement. "Swift and certain justice will be delivered to all those who would steal funds from citizens most in need."

A FEMA official told NBC News they recall being in a meeting with Tribble last year where she was touting the work of COBRA.

While Tribble does not work in Puerto Rico as a FEMA top official, she is "currently in a non-duty, non-pay status" with the agency, a FEMA spokesperson said.

Patterson was later hired by COBRA after helping steer contracts for the energy services company and misrepresented her FEMA salary in order to get a higher salary at COBRA, the indictment details.

FEMA told NBC News in a statement that the agency "cannot comment on personnel matters; however, the Agency is fully cooperating with federal investigators."

The Puerto Rico power authority also said the agency it is cooperating with the investigation, adding that the contracts worth over $1.8 billion were canceled back in March when they "became aware of possible irregularities involving efforts being carried out as part of Hurricane Maria's recovery process."

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