Updated to reflect fact WWE app has 17 million downloads, not WWE Network in the eighth paragraph. TheStreet regrets this error.

SANTA CLARA, Calif. (TheStreet) -- World Wrestling Entertainment (WWE) - Get Report is attracting more subscribers to its year-old WWE Network, but concerns about its ability to retain those followers is weighing heavily on investors.

Stamford, Conn.-based WWE announced that the WWE Network, which launched in February 2014, had surpassed 1.3 million subscribers, thanks in large part to the well-received WrestleMania, held on Sunday. Despite the boost in subscribers (WWE had just 1 million at the end of January), investors reacted negatively as the company said the figures could fall in the future following big events.

"We believe that exceeding 1.3 million subscribers reflects the successful execution of our strategy and puts us on the path to transformative growth through the WWE Network," said CEO Vince McMahon in a statement. The boost was aided by a free promotion in February, which added 201,000 trial subscribers, with 77% of them converting to paid subscribers in March.

The company noted it's going to invest in the Network, adding eight new shows this year. "It's easier to attract to talent now," McMahon said on the call. "It points to a lot of growth coming down the line."

"Over time, we continue to believe we can get the Network to have between three and four million paying subscribers," CFO George Barrios said on a conference call.

Investors, though, were disappointed by the numbers, with shares moving sharply lower, losing 16.7% to $13.76 in early afternoon trading Monday.

For the first quarter, WWE said it expects to end the first quarter with 918,000 subscribers on average, up 27% sequentially. WWE also said it expects Adjusted OIBDA (operating income before depreciation and amortization) to exceed the company's previous guidance of $3 million to $8 million in the first quarter.

First announced in January 2014 at the Consumer Electronics Show, the WWE Network is an over-the-top service, akin to Netflix (NFLX) - Get Report, except purely for wrestling fans. The service, which is available on the WWE app, costs $9.99 per month, and includes all of the company's pay-per-views, including WrestleMania. The WWE app already has more than 17 million downloads, according to the company.