Order unanimously reversed on the law without costs and motion granted. Memorandum: We conclude that it was an improvident exercise of discretion to deny plaintiffs' motion to amend their bills of particulars and to preclude the use of testimony by plaintiffs' expert at trial (see, CPLR 3025 [b]; Moore v. New York City Tr. Auth., 161 A.D.2d 505; Scarangello v. State of New York, 111 A.D.2d 798). When no prejudice or unfair surprise exists, leave to amend pleadings, or to supplement a bill of particulars, should be liberally granted. Defendants will sustain no actual prejudice by the proposed amendment because it constitutes only an embellishment of a theory of liability asserted in plaintiffs' initial bills of particulars (see, Scarangello v State of New York, supra).
Defendants, however, should be afforded the opportunity to conduct discovery with respect to the allegations raised by the amendment to the bills of particulars (see, Risucci v. Homayoon, 122 A.D.2d 260; Bernas v. Kepner, 36 A.D.2d 58; Maasch v. Corning Co., 29 A.D.2d 774; De Veaux v. Wide World Photos, 20 A.D.2d 787).