CHICAGO (CBS) — Two men once considered potential suspects in the alleged attack on “Empire” actor Jussie Smollett were moments away from testifying to a Cook County grand jury, before a last-minute phone call from Smollett’s defense team convinced prosecutors to postpone the testimony.

CBS 2’s Charlie De Mar has learned the brothers were waiting outside the grand jury chambers at the Leighton Criminal Courthouse on Tuesday, just minutes from testifying, when the Cook County State’s Attorney’s Office got a call from Smollett’s lawyers, claiming they may have new evidence.

Update from court confusion Monday: Multiple Sources: Brothers were expected to appear before Grand Jury. Last second phone call from Jussie Smolletts legal team claiming they possibly have new evidence calls off Grand Jury for the day. https://t.co/AF2To1whdb — Charlie De Mar (@CharlieDeMar) February 20, 2019

Prosecutors decided to postpone the brothers’ testimony, which would have been the first step toward indicting Smollett for filing a false police report.

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Ola and Abel Osundairo were arrested last week, but later released without charges. Sources said the two brothers told police they helped stage the attack with Smollett. They said they were paid $3,500 to pour a chemical on the actor, and place a rope around his neck, while yelling racist and homophobic slurs.

Two sources said they used a ride share vehicle to get to the Streeterville neighborhood, and were caught on camera appearing nervous.

The reported predawn attack on Jan. 29 is similar to what was depicted in a piece of hate mail sent to Smollet on the set of “Empire”. It depicts a stick figure with a noose around its neck.

Smollett still had a noose around his neck when police arrived on the scene of the alleged attack.

Sources say at least one of the brothers bought the rope used in the incident at Smollett’s request. The sources also say the “Empire” actor paid for the rope, which was purchased at the Crafty Beaver Hardware Store in the Ravenswood neighborhood the weekend of Jan. 25.

RELATED: Timeline Of Events In Jussie Smollett Case

Sources said one of the brothers held the rope and poured bleach while the other wore a plain red hat and yelled slurs at Smollett.

The sources say the red hat was bought at an Uptown beauty supply store and that the attack was supposed to happen before Jan. 29. The brothers told detectives the three men rehearsed the attack days prior to it happening.

The two brothers involved in the case told police Smollett also was behind creating the racist letter sent to the show, according to two sources with first-hand knowledge of the investigation.

When that letter did not get a “bigger reaction,” Smollett orchestrated the attack a week later with the two men, sources said.

Smollett received a letter containing a white powder Jan. 22. The letter was mailed to Chicago’s Cinespace Studios, where the show “Empire” is filmed. The letter prompted a HAZMAT response. CPD says the “white substance” was later determined to be aspirin.

The note was crafted with letters apparently cut out from magazines to form words. The pieced-together message contained racial and homophobic threats directed at Smollett. A magazine is one of the pieces of evidence retrieved from the brother’s home last week during a search conducted by CPD. Investigators also recovered a book of stamps.

Smollett repeatedly has denied staging the incident.

According to a source close to the investigation, after the brothers told police they conspired with Smollett, his lawyers told police he would not do a follow-up interview.

CBS 2 also has learned up to a dozen search warrants have been issued in the case, including for Smollett’s financial and phone records. Detectives are waiting for those records to come back.

On Tuesday, Smollett’s brother and sister posted Instagram messages appearing to criticize media coverage of the case.

“It will make the criminal look like he’s the victim, and the victim look like he’s the criminal,” read a quote attributed to Malcolm X.

Cook County State’s Attorney Kim Foxx has recused herself from the case, because she knows some of the potential witnesses. Acting State’s Attorney for the investigation will now be First Assistant State’s Attorney Joseph Magats.

Chicago police say the FBI is handling the investigation surrounding the letter because that’s a federal-level concern.

Meantime, Fox Television has denied rumors that Smollett is being written off of “Empire.”

“Jussie Smollett continues to be a consummate professional on set and as we have previously stated, he is not being written out of the show,” a statement from the company said.