The Securities and Exchange Commission said Friday that it has launched an investigation into the $700 million bid made in July for WPT Enterprises Inc. by professional poker player Doyle Brunson.

The unsolicited bid was nearly double WPT’s market capitalization and sent its stock price soaring 50 percent to an intraday high of $29.50 a share. L.A.-based WPT owns the World Poker Tour television show and traded at $6.14 a share by mid-afternoon Friday, down 1.4 percent.

The SEC said that Brunson and his Las Vegas law firm Goodman & Chesnoff prepared the bid that so the offer would expire before WPT had a chance to respond. The SEC’s investigation is focused on whether the offer violated anti-fraud laws.

Todd Steele, WPT’s chief financial officer, said the company will fully cooperate with any ongoing investigations but will not comment further.

The SEC filed an action this week in Fort Worth, Texas, to enforce subpoenas issued to David Chesnoff and Chaka Henry, two Goodman and Chesnoff attorneys who prepared and delivered the unsolicited offer.

The SEC said that Brunson invoked his Fifth Amendment right against self-incrimination, and that Brunson had told his attorneys to withhold documents and not testify.

The subpoena seeks to compel the attorneys to testify and provide documents in the case.

A call to Goodman & Chesnoff was not immediately returned.