Fallout has begun from Northwest Pipe Co.'s disclosure last week that it would delay the release of its third-quarter financial results with an indication that it might be facing a securities fraud lawsuit.

A Philadelphia-area legal firm said it is "investigating potential claims against" the Vancouver, Wash.-based producer of water transmission pipe and other tubular products in the wake of Northwest Pipe's announcement that it has postponed filing its financial results, pending conclusion of an accounting probe.

The law offices of Howard G. Smith, Bensalem, Pa., said its...