Republican nominee Donald Trump finally declared last week that he believes President Barack Obama was born in the United States. But in Arizona, longtime Maricopa County Sheriff Joe Arpaio still isn't convinced the president was born in the U.S.

Arpaio, who has been claiming for years that Obama's birth certificate is fake, told members of the Surprise Tea Party Patriots Tuesday that he was "not going to give up" on the investigation into the president's origins, the Arizona Republic reported. Arpaio added that Trump's declaration that Obama was American born didn't affect his probe.

"I don’t care where he’s from," Arpaio reportedly said. "We are looking at a forged document. Period."

Source: Graphiq

Obama was born in 1961 in Honolulu, but for years his opponents have been questioning whether he's a natural-born U.S. citizen — one of the requirements for the presidency. To tamp down the rumors, the White House released Obama's birth certificate in 2011.

Later that year, the Surprise Tea Party Patriots, an Arizona group that on its website calls for fiscal responsibility, constitutionally limited government and free markets, petitioned Arpaio to start looking into the veracity of the birth certificate. Already a divisive figure because of Justice Department allegations that he profiled and mistreated Latinos, Arpaio announced in 2012 that he thought the document was fraudulent, according to Politico.

"Based on all of the evidence presented and investigated I cannot in good faith report to you that these documents are authentic," Arpaio said at a news conference at the time. "My investigators believe that the long-form birth certificate was manufactured electronically and that it did not originate in a paper format as claimed by the White House."

That stance aligned him with Trump, who has been pressing Obama about the document for years. At one point, Trump offered to donate $5 million to charity if Obama would provide additional records from his college years.

But Trump gave up the birther cause Friday, saying at a news conference that "President Barack Obama was born in the United States."

Arpaio, who spoke on Trump's behalf at the Republican National Convention earlier in the year, was undeterred as he confirmed he was extending the investigation. "I know all the politicians say, 'Sheriff, don’t talk about it,'" the  reported he said Tuesday. "But how can I back down when we started it? I’m not going to just forget it."