Mueller's most recent search warrant in Manafort case includes information related to 5 telephone numbers

Within the last four weeks, special counsel Robert Mueller’s team informed lawyers for Paul Manafort that they obtained a search warrant for five telephone numbers controlled by AT&T.

The special counsel, which is investigating whether or not the Trump campaign colluded with Russians in the 2016 election, revealed in court filings late Thursday that a search warrant was issued on March 9 in the Manafort case. This most recent warrant suggests that the Mueller investigation is still very active as they continue to seek new information in their probe of both the former Trump campaign chairman and beyond.

The filing states that the March 9 affidavit “contains redactions — albeit more substantial ones — relating to ongoing investigations that are not the subject of either of the current prosecutions involving Manafort.”

It's unclear if that refers to a broader, as-yet-unknown investigation of Manafort or someone else entirely.

The new search warrant was revealed as part of a filing opposing a request by Manafort’s lawyers to produce unredacted search warrant affidavits to the defense.

Mueller’s team did not reveal precisely what it was seeking with the warrant, but according to ABC News Consultant and former FBI Special Agent in Charge Steve Gomez, “From a warrant like this, prosecutors could possibly obtain subscriber information, toll records, geo-location information and potentially content, including text messages and emails.”

Altogether, the government outlined in the new court document seven search warrants against Manafort. Investigators searched three bank accounts, his Virginia residence, a storage locker, three e-mail accounts, and a hard drive.

It's unclear if the new information could lead to new charges against Manafort, who was indicted for conspiracy, money-laundering, tax evasion, and other charges -- but the actions by the investigators are likely to ratchet up pressure against the former Trump campaign chairman.

Manafort has tried to get the charges against him thrown out, challenging the broad scope of the Mueller investigation as amounting to a "blank check." But the special counsel, in its reply to the court this week, defended its authority, and in doing so disclosed a memo written last summer by Acting Attorney General Rod Rosenstein affirming that Mueller’s jurisdiction covers Manafort’s activity in connection with Ukraine, for which he is now under indictment.

The memo empowered Mueller to investigate allegations that Manafort “committed a crime or crimes by colluding with Russian government officials with respect to the Russian government’s efforts to interfere with the 2016 election ...”

The new search warrant against Manafort came just two weeks after former longtime Manafort business partner Rick Gates -- Trump's deputy campaign manager -- pleaded guilty and is now cooperating in the Mueller probe.

In addition, government prosecutors recently revealed -- in a pre-sentencing filing for another case in their purview -- that a business associate of Manafort and Gates was assessed to have ties to Russian intelligence.

Prosecutors allege that this associate was talking to Gates in the run-up to the 2016 election, though the subject of the alleged conversations was not revealed. The court filing also stated that the conversations were "pertinent" to the government's investigation, though nothing more specific was added.