12:45 PM PT -- Tekashi 6ix9ine's lawyer, Lance Lazzaro, tells TMZ ... Tekashi was notified 2 weeks ago he violated the terms of his probation. He was ordered to appear before a federal judge today in New York ... but he was an hour late to the hearing -- and the judge dispatched U.S. Marshals to find him.

Lazzaro says Tekashi arrived on his own and surrendered voluntarily.

Lazzaro says there were 3 violations, according to the government -- Tekashi performed in Las Vegas, Nevada without permission from his probation department ... Tekashi failed a drug test, testing positive for meth ... and also failed to take a required drug test at another time.

Lazzaro says testing positive for meth could be a false positive -- he says Tekashi takes Adderall.

Tekashi 6ix9ine is back in hot water ... he was arrested today for violating the terms of his supervised release.

TMZ has obtained the court order, revealing the rapper -- whose real name is Daniel Hernandez -- was taken into custody Tuesday morning. He’s set to be arraigned later this afternoon at a NYC federal courthouse for allegedly violating the conditions of his supervised release.

We spoke with his lawyer, Lance Lazzaro -- but the exact nature of the alleged violation or violations is still unknown.

Tekashi’s original plea deal in 2020 was no walk in the park, after he was hit with various charges for racketeering, firearms offenses, conspiracy, narcotics trafficking, and a laundry list of other crimes.

As we previously reported, he avoided a hefty 47-year prison sentence by agreeing to cooperate with the authorities and help with their investigation of other defendants.

After getting his ankle monitor removed at the end of his home confinement in 2020, Tekashi was still on a tight leash per the terms of his 5-year period of supervised release, and had a schedule of check-ins with his probation officer.

At the time of his Tuesday arrest, Tekashi was still on supervised release.

Just 3 weeks ago, Tekashi told us he wasn't worried about his new record deal's clause about staying out of trouble ... claiming he's a "squeaky clean" individual, and insisting that trouble just has a knack for finding him "all the time."