Federal officers descended on Skid Row in downtown Los Angeles Thursday morning as part of a stunning investigation into voter fraud following LA’s mayoral election.

About 20 agents swooped in on the notoriously blighted area after homeless people iving there claimed they’d been paid cash to sign multiple registration forms, forge signatures and fill out voter information.

The California Post saw group of three plainclothes agents fanning out across Skid Row’s rundown streets just before noon, interviewing dozens of people and taking notes.

The officers — dressed in jeans, sweatshirts and baseball caps — spoke to locals who appeared to point them in the direction of where to look.

The Department of Justice confirmed that federal agents were investigating a criminal matter, but declined to comment further. The FBI said it does not comment on ongoing investigations.

The action comes after series of shocking videos emerged a week after Election Day featuring Skid Row residents claiming they were paid to vote for incumbent Mayor Karen Bass and councilwoman Nithya Raman, who edged out insurgent candidate Spencer Pratt in the primary.

In one of the clips, a man claimed he received $4 to vote for Bass.

When asked whether he would also have been paid to vote for Raman, he answered “yes” and said Pratt was not among the candidates he was encouraged to support.

“They gave you an optional choice,” claimed the voter, Kevin Shepherd, alleging he was offered $2 but negotiated for a higher payment. He further claimed that he completed a mail-in ballot for Bass and deposited it in a ballot box.

The California Post was unable to independently verify the claims made in the videos.

The footage, which was provided to the Department of Justice, followed The Post’s revelations that thousands of homeless people were registered to vote in shelters they didn’t live in.

A review of records by The Post identified more than 7,600 registered voters linked to shelters and other social service entities, including 1,160 registrations connected to the Midnight Mission in Skid Row.

A homeless services drop-in center in Venice had 185 registered voters tied to its address. The organization received a $600,000 taxpayer-funded grant awarded by Raman while she chaired the City Council’s Housing and Homelessness Committee.

Garrett Fahy, an attorney who practices election law in California, said the registrations identified during the Post’s review reflect how the state’s election system is designed to operate.

He said the concentration of voters registered through shelters, service providers and other nontraditional addresses should be viewed within the broader framework of California election law.

“This is the system that our representatives have given to us,” Fahy said. “If you don’t like our system, don’t yell at your local elections official.”

Days before the bombshell Skid Row revelations emerged, the city’s top federal prosecutor announced his office was pursuing several election fraud investigations with the FBI as questions swirled over California’s sluggish vote count.

First Assistant U.S. Attorney Bill Essayli said he was working with the Department of Justice “to conduct a comprehensive audit of California’s voter rolls” three days after the June 2 election.

A federal prosecutor visited the LA County ballot processing facility the same day, touring the center amid growing questions about the speed of ballot processing.

Bass handily won the mayoral primary, with Raman coming in second place after a late surge propelled her past Pratt despite his strong Election Day showing.

Representatives for Bass, Raman and Pratt did not immediately respond to requests for comment.