Oregon-based Columbia Helicopters called off its planned sale Monday after the would-be buyer reported “material weakness” in its own internal controls over financial reporting.

The Bristow Group paid Columbia a $20 million breakup fee, consistent with terms of the transaction announced last fall.

“We move on. Our business is strong as a private company so we will continue doing what we do,” said Santiago Crespo, Columbia’s vice president of business development and strategy. He said it’s too soon to say whether Columbia will seek another buyer.

“That decision would be made sometime in the future,” Crespo said.

Columbia and Bristow announced their $560 million deal in November, but it has been in trouble for weeks. Bristow’s stock lost more than two-thirds of its value after it announced the deal for Columbia and investors publicly questioned the Texas company’s ability to finance the transaction.

As recently as last month, though, Columbia insisted it would go ahead with the deal.

Bristow delayed reporting its quarterly results without explanation last week. On Monday the company alerted investors that its financial results for its last fiscal year are not reliable.

“Management has concluded that the company did not have adequate monitoring control processes in place related to non-financial covenants within certain of its secured financing and lease agreements,” Bristow said in a written statement.

Bristow’s shares fell nearly 12 percent in after-hours trading Monday after the company announced its accounting issues and scuttled its deal with Columbia.

About half of Columbia’s employees work in Oregon. The company operates heavy-lift Chinook helicopters for defense, firefighting and natural resource exploration.

Columbia is owned by the family of company founder Wes Lematta, who died in 2009. It says sales totaled $281 million in the 12 months ending last September.

-- Mike Rogoway | twitter: @rogoway | 503-294-7699