Following a trail of evidence that involved conversations about angry cocaine customers and postal tracking numbers, the FBI busted a massive drug ring in Pontiac on Friday, raiding homes, arresting dealers and seizing heroin, fentanyl, coke and crystal meth by the kilos.

According to court documents, the FBI and federal prosecutors, the Pontiac-based drug organization had operators all over the country, including in Indiana, West Virginia and Tennessee. Prosecutors said the drugs came from Mexico by way of Phoenix and made their way to Michigan through the U.S. Postal Service.

The tracking numbers on the packages and surveillance video from at least one post office helped the FBI close in on the drug dealer suspects, including some who talked about their upset customers. In court documents, a federal agent wrote that the drug ring had obtained "a lesser-quality narcotics that led to customer complaints."

And the sellers talked about it.

"What did you do with that stuff? You just set it to the side?" one suspect said to another in a conversation that was detailed in court records.

"Yes. Nobody wants it," the other replied, later adding that he can sell it for $50 or $40 a gram to get rid of it, court records state.

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Then there's another conversation, court records show, where two suspects talk about customers complaining about "lesser-quality" drugs. One tells the other to make the drugs "as strong as he could," and that if he gets too many complaints, he won't sell it anymore.

The FBI also obtained surveillance camera video from a post office in Arizona, where a Lansing man was seen mailing a package to Clinton Township. It had an expected delivery date of March 25, but was intercepted that same day. Inside the package was about 4½ kilos of suspected drugs, packaged in four separate items: three brick shaped-items wrapped in silver packaging tape; and one brick-shaped item wrapped in silver and black tape.

The suspected drugs were taken to the Oakland County Sheriff's Laboratory for testing and confirmed to be 3 kilograms of fentanyl and 1 kilogram of cocaine.

A review of surveillance video at the post office in Arizona revealed the following individual as the sender of the package: Neil Thomas, 61, of Lansing, a repeat offender with previous felony convictions involving heroin, money laundering and drug manufacturing.

In a criminal complaint unsealed Friday, Thomas was charged with attempted possession with intent to distribute controlled substances. Other defendants charged in the case include:

David Thomas, of Indianapolis; Anthony Knight, who has a previous felony conviction for criminal sexual conduct and drug distribution; Henry Thomas, who has prior felony convictions involving cocaine and heroin; Marlon Jackson, who has previous felony convictions for armed robbery, selling heroin, larceny and being a felony habitual offender.

According to FBI spokesperson Mara Schneider, the agency executed search warrants at multiple homes that led to the arrests of multiple defendants. Search warrants also were executed in other states involving the same drug organization.

The raids coincided with the unsealing of federal complaints against the defendants, who are allegedly linked to the multistate ring, which had "significant longtime operations based in the Pontiac/Oakland County area," authorities said.

During the investigation, law enforcement officers seized 2½-3 kilograms of cocaine that was shipped from Phoenix to Pontiac, and seized 4 kilograms of fentanyl and cocaine on March 26 that was shipped from Phoenix to Clinton Township, according to a federal complaint.

The raids in metro Detroit were handled by the FBI-led Oakland County Gang and Violent Crimes Task Force, which includes members from several law enforcement agencies.

Oakland County Undersheriff Mike McCabe referred questions to the FBI.

Contact Tresa Baldas: tbaldas@freepress.com. Follow her on Twitter: @Tbaldas.