More than 50 employees at Asahi Kasei Construction Materials Corp. manipulated data in at least 266 piling projects the contractor undertook over the past 10 years, its parent Asahi Kasei Corp. announced Friday.

This suggests data falsification was pervasive at the subcontractor, contradicting the firm's earlier claim that a single employee may have been responsible.

"We feel sincerely sorry for the fact that this many people were involved in this many projects, and for allowing such (misconduct) to happen," Masahito Hirai, vice president of Asahi Kasei, told a packed news conference in Tokyo.