Regulators have ordered the owner of a D.C.-based online trading company to stop raising money after accusing the firm of fraud that threatens the investments of nearly five dozen people — mostly professional basketball and football players.

A complaint issued late Wednesday by the Financial Industry Regulatory Authority alleges that Success Trade Securities and its founder misrepresented or omitted key facts when it borrowed more than $18 million from 58 investors starting in March 2009.

The complaint did not name the investors but said most were current or former NFL and NBA players. The investors were promised returns of at least 12.5 percent, and sometimes up to 26 percent, according to Finra, a self-regulatory body that oversees broker dealers.

But the company and its founder, Fuad Ahmed, used the money in ways that were not disclosed to investors, the complaint said. Investors did not know that roughly $4 million borrowed from some of them was used to pay the monthly interest owed to other investors or that their proceeds paid the $1,300-a-month lease on Ahmed’s Range Rover.

Finra also alleges that Ahmed used $800,000 to cover his credit card bills, travel and other personal expenditures. Investor proceeds also went toward an $82,000 interest-free loan for Ahmed’s brother, Finra alleges.

The regulatory body filed an order to halt the activities while it investigates. Ahmed and the company agreed to the order without admitting or denying guilt. The group can fine the firm or bar Ahmed from the securities industry, depending on the outcome of the probe.

Ahmed said Thursday that he intends to vigorously defend himself and the company.

“There is a misunderstanding that needs to be cleared up,” said Ahmed.

Ahmed said his firm has real value, including the trading technology it has developed and continues to enhance. “We intend on licensing this trading technology to other firms, and that will produce additional revenue,” he said.

Ahmed founded Success Trade Securities in 1998 after working for several broker dealers, including Smith Barney. He gained national attention in 2007 with the launch of Just2Trade, a discount online trading business that aimed to compete with better-known names such as E-Trade by charging much lower fees. That business won accolades from the financial press and is included on Barron’s 2013 list of the best online brokers.

But Just2Trade and LowTrades, the two divisions of Success Trade Securities, did not generate enough revenue to cover the company’s expenses, the complaint said. Together, they had about half of the business necessary to be profitable. The parent company, Success Trade, relied almost exclusively on loans from investors — through promissory notes — to keep its subsidiaries solvent.

Without the revenue needed to operate the business and pay the interest owed to investors, the company kept selling more promissory notes. It raised $18 million after leading investors to believe it was only raising $5 million, the complaint said.

Athletes were the main source of the loans, and Success Trade Securities got to know them through an investment advisory firm in McLean called Jade Private Wealth Management, or JPW. On its Web site, JPW says it specializes in “developing and maintaining a well thought out wealth accumulation plan” for professional athletes.

The complaint does not accuse JPW of wrongdoing. The company remains an independent contractor of Success Trade Securities and operates out of the trading company’s McLean office, the complaint said. Of the 15 people employed by Success Trade Securities, three of them also work for JPW.

“Typically, investors were introduced to [Success Trade] through JPW,” and nearly all the investors in the trading firm were clients of JPW, the complaint said.

JPW is cooperating with the investigation, said Jacob Frenkel, who represents JPW in this matter. The company “feels confident that the introductions, recommendations and asset management strategies it advanced for its clients were and are in their best interests,” Frenkel said. “Nevertheless, they’re troubled and disappointed by the allegations against Success Trade.”

The complaint did not say how much money investors lost, if any.

But it said that when the promissory notes started to mature in November, about three years after they were issued, Ahmed allegedly knew that the company did not have the funds to pay back the principal. He asked some note holders to extend the terms of their notes at a higher interest rate. He asked others to convert their notes into stock. At least five took him up on the offers.

Ahmed led them to believe he would acquire an Australian online broker-dealer for $15.6 million in cash by April and publicly list his firm’s stock on a foreign exchange, the complaint said. But as of April 4, the parent company had only $25,000 in the bank.