Tekashi 6ix9ine Got Immediately 'Gangsta Checked' Upon Arrival in Prison

Tekashi69 isn't getting the red carpet treatment in federal lockup -- several Crips wasted NO time "gangsta checking" him, and TMZ has learned that's what got him transferred to a new facility.

The tense showdown went down November 19 at Brooklyn's Metropolitan Detention Center, right after 6ix9ine was denied bail ... according to our law enforcement sources.

We're told Tekashi, an alleged member of the 9 Trey Gangsta Bloods, was confronted by inmates affiliated with the Crips who were in the intake area as he arrived. That's when one inmate 'G Checked' him -- meaning stepped up to him to see if he's a real gangsta or just a wannabe.

We're told the Crip told Tekashi he better understand who's in charge -- and the only thing that saved him from a beatdown was the fact prison staffers quickly intervened.

His attorney, Lance Lazzaro, says 6ix9ine "was being threatened in jail. However, he was not scared nor did he request being removed. The [Bureau of Prisons], acting upon these threats, removed him to a different facility to eliminate the threat."

TMZ broke the story ... the new facility where he ended up is sometimes used for witnesses who cut deals. Our sources said Tekashi specifically asked to be in a unit away from Crips and Bloods.