[28 U.S.C.] Section 1446(b)(1) and (b)(3) specify that a defendant must remove a case within thirty days of receiving from the plaintiff either an initial pleading or some other document, if that pleading or document shows the case is removable. However, these two periods do not otherwise affect the time during which a defendant may remove. That is, the two periods specified in § 1446(b)(1) and (b)(3) operate as limitations on the right to removal rather than as authorizations to remove.
We hold that a defendant who has not lost the right to remove because of a failure to timely file a notice of removal under § 1446(b)(1) or (b)(3) may remove to federal court when it discovers, based on its own investigation, that a case is removable.
Slip op. at 3-4.
In other words, the two thirty-day time periods listed above are not the only times that a defendant may remove a case under CAFA, and a defendant may not remove "if and only if" the initial pleading or other document shows grounds for removal. Rather, a defendant may remove based on independent information gathered outside these thirty-day periods, provided that it has not previously waived the right to remove by failing to do so where the plaintiff's initial pleading or other document shows that the case is removable.
Roth v. CHA Hollywood Medical Center is available here.