“It was all over drugs,” said a former investigator who worked the case.

One of the men, Ronald Washington, had long been suspected of being involved in the hip-hop pioneer’s execution-style murder in his Queens studio, the source said.

Jay, 37, whose real name was Jason Mizell, was believed to have ponied up $15,000, while a pal put in another $15,000, to buy a total of 2 kilos of coke that the pair then planned to turn around and peddle.

Mizell was new to the drug world and just hoped to score a quick buck, sources told The Post around the time of his murder.

But intermediaries who were friends of Mizell instead allegedly took both the cash and drugs and split.

When the drug suppliers still demanded their dough, Mizell balked at paying any more, sources said.

“He said he got robbed, [too], and couldn’t pay them back,” the former prober said.

“After awhile, [the suppliers] said, ‘F–k it,’ and killed him,” the source said. “It looked like he had no way or intention of paying them, and they f–king shot him.

“It was always over drugs and money owed,” the source said. “They all knew each other.”

Mizell’s killers had been buzzed into his Jamaica studio that day because they were known from the neighborhood, the ex-investigator said.

There were three witnesses who saw them, the source said — although the witnesses were all reluctant to speak. One of them eventually identified Washington as one of the people buzzed in, but it wasn’t enough for an arrest at the time, the source said.

The name of the second suspect, Karl Jordan Jr., eventually also landed on investigators’ radar because he had a relative who was a drug dealer, the source said.

When the feds first took over the case, they thought the slaying was tied to a robbery team that had been targeting southeast Queens and Long Island, the source said.

But then it quickly became clear “it was always over drugs and money owed,” the source said.

Washington is already behind bars for robbery, while Jordan, 36, was nabbed Sunday, sources said.