Arizona’s Maricopa County Sheriff Joe Arpaio still isn’t convinced President Barack Obama was born in the United States.

Arpaio, a supporter of Republican presidential nominee Donald Trump, told a tea party group Tuesday he’s still investigating Obama’s birth certificate, which the president made public in April 2011.

“I don’t care where he’s from,” Arpaio told the crowd, according to USA Today. “We are looking at a forged document. Period.”

Brian van der Brug via Getty Images Sheriff Joe Arpaio is still a birther.

“I know all the politicians say, ‘Sheriff, don’t talk about it,’” he continued. “But how can I back down when we started it? I’m not going to just forget it.”

Trump, who questioned Obama’s birthplace for years, finally admitted last week Obama was born in the United States. While making that statement, he blamed Democratic presidential nominee Hillary Clinton for starting the birther movement. (She did not.)

Arpaio endorsed Trump for president in January. Trump touted the endorsement, citing Arpaio’s push for stricter border control.

“This is a man when we talk about borders, this is a man that believes in borders and getting his endorsement means a lot to me,” Trump said.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.