It should have been apparent to Allianz that all of the information it needed to issue a denial of coverage was contained in the enclosures forwarded by the Transit Authority along with its notice of the accident, including that the Transit Authority's claim arose out of the work of Allianz's named insured, that the injured person was an employee of the named insured, and that the Transit Authority's notice of the accident was untimely. Accordingly, Allianz's nearly four-month delay in disclaiming coverage, measured from its receipt of the Transit Authority's notice of the accident, was unreasonable as a matter of law, absent a reasonable explanation for the delay ( see First Fin. Ins. Co. v Jetco Contr. Corp., 1 NY3d 64, 68-69, 70). It does not avail Allianz to argue that it was not required to limit its investigation to the Transit Authority's delay, where its claims examiner could not say, at her deposition, what other grounds for denying coverage were investigated.