Barbie dolls in the Mattel display at the annual Toy Fair in New York.

Mattel shares cratered on Friday after the toymaker said Thursday it would pull a bond sale because of "an anonymous whistleblower letter."

The company was made aware of the anonymous letter on Tuesday, according to a filing. Mattel said it is terminating the sale of senior notes due in 2027 "to provide the company with an opportunity to investigate the matters set forth in the letter."

The company did not disclose the contents of the letter. Mattel declined to comment further.

Shares of the company closed down Friday, falling 15.7% to $11.31.

The sale, which was worth an estimated $250 million, had initially be scheduled to close on Thursday. Mattel said it intends to refinance bonds that are due in October 2020 prior to maturity.

Mattel has about $3 billion in debt on its books, with about $250 million of which is due next year.

Shares of Mattel had risen 34% since January ahead of Mattel's filing. However, the stock is down around 14% from the same time last year.

The Securities and Exchange Commission declined to comment.

— CNBC's Courtney Reagan contributed to this report.