China Construction Bank Corp., the nation’s third-largest commercial lender, was accused in a US lawsuit of enabling a massive fraud in the reinsurance industry that left companies with “monumental losses” and sinking stock prices.

The bank allowed employees to conspire with Israeli insurance startup Vesttoo Ltd. to sell reinsurance policies that weren’t real, according to a complaint filed late Thursday by the Porch Group in Manhattan federal court.

Vesttoo filed for Chapter 11 bankruptcy in August after it was accused of using some $2 billion of fraudulent letters of credit.

The Porch Group said that its unit Homeowners of America Insurance Co. lost tens of millions of dollars when its purported $300 million letter of credit proved worthless.

“Not only did HOA incur colossal losses, but news of its exposure to the fraud perpetrated by Vesttoo and CCB shocked the market and imposed severe losses on Porch Group’s shareholders as its stock price plummeted,” according to the suit.