Downloads of Robinhood and several other stock trading apps soared last week as investors rushed to buy shares in video game retailer GameStop, AMC cinemas, and other shaky businesses.

Over 2 million people downloaded Robinhood’s app last week on Apple’s App Store and the Google Play store combined, representing a 394% increase from the previous week, according to analytics firm Sensor Tower. 

The last time Robinhood experienced such explosive growth was in March during the onset of the coronavirus pandemic and ensuing stock market turmoil, said Sensor Tower head of mobile insights Randy Nelson. Over 2 million people downloaded Robinhood’s app in all of March, Nelson said, and while that was a record for the company at the time, it pales in comparison to its current growth. 

“It’s really unprecedented,” Nelson said.

While Robinhood was the most downloaded trading app in last week, similar apps also had huge gains.

Last week, over 1 million people downloaded China-owned trading app Webull, a 751% increase from the previous week. Meanwhile, downloads of Fidelity’s app grew nearly 900% to 668,000.

Nelson suspected that investors downloaded apps like Webull and Fidelity as alternatives after Robinhood blocked people from buying shares in suddenly hot but beleaguered companies including GameStop.

For its part, Robinhood isn’t currently running many mobile ads to promote its app, despite its rising popularity, according to Nelson.

Sensor Tower also monitors the number of times a company’s ads appear on services like Facebook and YouTube. Robinhood’s ad impressions, as the measurement is commonly known, increased after March when the company experienced its first surge in downloads, Nelson said, implying that the company had tried to capitalize on its momentum.

But Robinhood’s most recent user boom ended up being a problem that forced it to raise billions of dollars to cover the rising operating fees that accompanied the influx of new users and trades.

Robinhood competitor Webull, on the other hand, has opened up the floodgates of advertising in recent weeks. During the last three days of January, it was the top advertiser on Facebook’s network in terms of ad impressions, Nelson said.