at the time of the attack or should have inquired into the actions of the police officers at that time. In response, Piotrowski alleges that the police officers took active steps to suppress any information concerning their prior knowledge of the threat. When a defendant controls the facts surrounding causation such that a reasonable person could not obtain the information even with a diligent investigation, a cause of action accrues, but the statute of limitations is tolled. See United States v. Kubrick, 444 U.S. 111, 122, 100 S.Ct. 352, 359, 62 L.Ed.2d 259 (1979) (tolling limitations period where “the facts about causation may be in the control of the putative defendant, unavailable to the plaintiff or at least very difficult to obtain.”); Frazier v. Garrison I.S.D., 980 F.2d 1514, 1521-22 (5th Cir.1993) (affirming summary judgment on limitations grounds, stating that: “No facts indicate to us that the alleged discrimination was either hidden or for some reason not apparent to a reasonable prudent person,” and contrasting to scenario in which defendant’s actions would not lead a reasonably prudent person to suspect critical facts and investigate further). Consequently, we cannot say as a matter of law that the limitations period started in 1980.13 Thus, if Piotrow-ski’s “state-created danger” theory raises a cognizable constitutional claim under § 1983, the district court erred in determining that her suit was time-barred.
C
We need not decide, however, whether Piotrowski’s “state-created danger” claim is a cognizable § 1983 theory that is not time-barred. Even if she has alleged a “state-created danger,” she has failed to allege facts that implicate the City itself. A municipality does not incur liability under § 1983 “unless action pursuant to official municipal policy of some nature caused a constitutional tort.” Monell v. Department of Soc. Servs., 436 U.S. 658, 691, 98 S.Ct. 2018, 2036, 56 L.Ed.2d 611 (1978); see also City of Canton v. Harris, 489 U.S. 378, 385, 109 S.Ct. 1197, 1203, 103 L.Ed.2d 412 (1989) (“[0]ur first inquiry in any case alleging municipal liability under § 1983 is the question whether there is a direct causal link between a municipal policy or custom and the alleged constitutional deprivation.”); Leffall, 28 F.3d at 525 (requiring allegation that policy or custom was “a cause in fact of the deprivation of rights inflicted”); Colle v. Brazos County, 981 F.2d 237, 244 (5th Cir.1993) (“[0]nly when the execution of a county’s policies or its customs deprives an individual of constitutional or federal rights does liability under § 1983 result.”).
Piotrowski alleges that the police officers increased the threat to her life, but she does not allege that the increased danger resulted from the City’s policies. Nowhere in her substantive due process claim does Piotrowski allege that a causal link existed between a City policy or custom and the alleged state-created danger. Rather, she alleges that the increased danger resulted from the actions of certain police officers. Because the City cannot be held liable under a respondeat superior theory, Monell, 436 U.S. at 691, 98 S.Ct. at 2036, Piotrowski has failed to allege facts supporting a § 1983 claim against the City.
Ill
For the foregoing reasons, we AFFIRM the dismissal of Piotrowski’s suit. We modify the district court’s judgment, however, to dismiss without prejudice to Piotrow-
13
Nor can we say as a matter of law that the limitations period did not start until January, 1993, when Piotrowski learned of the police officer’s deposition. Although she acquired actual knowledge of the facts at that time, the City suggests that she could have obtained that information earlier. The lawsuit for which the 1993 deposition was taken concerned libel and slander claims brought by the police officers against the author of a book written about Piotrowski’s case. The author acknowledges in the book that Pio-trowski helped her develop the book. Alleging that the book discussed at least some of the relevant actions of the police officers, the City suggests that Piotrowski either knew or should have known of the police officers' actions prior to the 1991 publication of the book. Determining the validity of the City’s contention, however, would require us to go beyond the pleadings, and we will not entertain it at this time.