Shares of Fitbit Inc jumped as much as 8% after a previously unknown entity calling itself ABM Capital said it had offered to buy the wearable device maker but gave up some of those gains after the company denied receiving any offer.

Fitbit said it had not received any communication from ABM Capital or any other firm regarding a reported offer, a spokesperson for the company said in an email.

Reuters was not able determine the veracity of the offer.

The filing, which contained little detail of the purported offer to buy the company for $12.50 per share, listed a Shanghai address for ABM Capital and also had a typographical error in Fitbit’s name.

“We are skeptical of a deal consummating given legitimacy concerns around ABM Capital,” Mizuho Securities analyst Betty Chen wrote in a note.

Reuters was unable to reach ABM with the telephone number provided in the filing.

The U.S. Securities and Exchange Commission (SEC), which received the filing, declined to comment.

A search on the securities regulator’s public Edgar database did not show any other previous filings from ABM Capital.

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Concerns about the security of Edgar, where thousands of public companies and money managers make official filings, were raised last year when a firm calling itself PTG Capital Partners offered to buy cosmetics maker Avon Products Inc.

In another instance, a group identifying itself as shareholders of U.S. chipmaker Integrated Device Technology Inc earlier this year offered to buy the company for $32 per share.

Fitbit’s shares fit were up 3.8% at $8.88 in afternoon trading, well below the purported offer price of $12.50. The stock had risen as much as 8% earlier in the session.

The purported offer represents a premium of 46.2% to the stock’s Wednesday close.

The New York Stock Exchange had halted Fitbit’s shares at 11:02 a.m. ET for volatility.

Shares of the company, which had a market value of $1.91 billion, had lost about 70% of their value this year through Wednesday’s close.