Shares of Mattel (MAT - Get Report) were sliding more than 10% Friday after the toymaker decided to cancel a $250 million debt offering because of a mysterious whistleblower letter.

Mattel said it became aware of the letter on Tuesday, according to a regulatory filing with the Securities and Exchange Commission.

The company, which makes the Barbie brand of dolls among many other products, didn't disclose the contents of the whistleblower letter but said it needed to cancel the debt sale in order "to investigate the matters set forth in the letter," the SEC filing stated.

Mattel shares tumbled 10.24% to $12.06 on Friday.

Constable owns none of the securities listed in this story.