(Reuters) - Toyota ( TM ) has been sued in a proposed U.S. class action accusing the Japanese automaker of emissions cheating in nine engines for its forklift trucks.

A complaint was filed by forklift purchasers on Sunday night in San Francisco federal court against Toyota ( TM ) and its affiliate Toyota Industries ( TYIDF ), the world's largest maker of forklift trucks.

It came after an internal Toyota ( TM ) probe found in January that the company sometimes made software changes or substituted different engines in emissions tests, enabling forklifts to perform better there than in the real world.

Toyota ( TM ) suspended some forklift sales in Japan in March 2023 because of emissions issues.

But the plaintiffs said its misconduct first surfaced after an inquiry from the U.S. Environmental Protection Agency, though U.S. regulators have not brought any enforcement action.

"Toyota ( TM ) has tried to limit the damage to Japan," but its "toxic culture of fraud, negligence, and noncompliance" undermined forklift engine certifications in all markets, including the United States, the complaint said.

Toyota ( TM ) had no immediate comment on Monday. Lawyers for the plaintiffs also had no immediate additional comment.

The plaintiffs are Broadmoor Lumber & Plywood, Marders and Ferraro Foods, which are respectively a South San Francisco landscaping supply company, a Bridgehampton, New York, nursery, and a Piscataway, New Jersey, distributor of Italian food.

All said they would not have bought Toyota's ( TM ) forklifts had they known the vehicles did not meet emissions standards, and would perform worse than advertised.

The lawsuit seeks unspecified compensatory and punitive damages, and full refunds.

Toyota's ( TM ) internal probe found that the engine division at Toyota Industries ( TYIDF ) had a "contractor's mentality" and a climate of "trivializing industrial vehicles," which left executives with "low risk sensitivity" to emissions rules.

The case is Broadmoor Lumber & Plywood Co et al v Toyota Industries Corp ( TYIDF ) et al, U.S. District Court, Northern District of California, No. 24-06640.