US securities regulators on Thursday suspended trading in a seemingly defunct company whose shares had attracted the attention of investors over the past two months.

The decision by the Securities and Exchange Commission to bar trading in SpectraScience, a Minnesota healthcare company, comes as new and inexperienced retail traders have flooded into the country’s $45tn stock market, drawing scrutiny from policymakers in Washington.

The SEC said social media accounts may have been used in a co-ordinated attempt to “artificially influence” the share price of the company, which does not have a working phone line or website and has not filed quarterly financial results since 2017.

Trading of the company’s stock picked up suddenly in December and continued at elevated levels. On January 28, the day a retail-fuelled rally sent the stock of retailer GameStop to a record high, more than 3bn shares of SpectraScience changed hands.

The avalanche of orders pushed SpectraScience shares briefly above half a penny, its highest level in more than four years. The company’s stock last traded above a penny in 2015.

Line chart of Number of shares traded each day (bn) showing Trading in SpectraScience explodes

US securities regulators have sharpened their gaze on the recent spurt of trading by retail investors, including many Americans who are relatively new to the stock market. In an alert last month, the commission warned that jumping “on the bandwagon” could result in “significant investment losses”.

The House of Representatives next week will hold a hearing on the volatility in financial markets, and has called Vlad Tenev, the chief executive of the online broker Robinhood, to testify. Robinhood has become one of the go-to platforms for new traders, many of whom piled into stocks like GameStop, AMC and BlackBerry in January.

The SEC said the suspension in SpectraScience shares would last to February 25.

“The commission is of the opinion that the public interest and the protection of investors require a suspension of trading in the securities,” Vanessa Countryman, the secretary of the SEC, wrote in the commission’s order.

Some activity appears to have been orchestrated via social media platform Twitter, where clusters of day trader accounts tagging the SpectraScience ticker symbol — SCIE — spoke in bombastic terms about the stock and their recent investments as they discussed so-called ‘penny plays’.

One account under the name Alexander Delarge, which had amassed around 50,000 followers, tweeted a post encouraging users in late January to buy the stock, adding that it was likely to go to $1.

“Ill be buying a million shares at a Dollar showing my buy order to keep it going! As we all should!” the user wrote.

Among later tweets by the same account, one showed a screenshot of a portfolio of 5.5m SpectraScience shares saying it had gained 50 per cent in one day, adding: “Let the haters watch when this blasts off!”

Another highly-followed day trader account by the name of Canadian Jennifer, also joined the chorus in early February. “Yes I bought more! I’m not telling you to buy it. I’m just posting what I SEE and that I’m holding. When my instincts kick in I listen,” the user wrote