The shares of cryptocurrency miners Marathon Digital Holdings, Inc. and Hut 8 Mining Corp. surged Tuesday as bitcoin’s price reached $50,000 for first time since early September.

The stocks, which often move in tandem with the largest cryptocurrency’s price, have steadily advanced since hitting lows in September, when prices for bitcoin slumped to near $40,000.

Marathon Digital rose 6.2% and Hut 8 Mining advanced 4.5%, leading gains in the sector. Bitfarms Ltd. climbed 4.2%, Hive Blockchain Technologies Ltd. was up 2.5% and Riot Blockchain, Inc. increased 2% in U.S. trading. The Canadian-listed miner Galaxy Digital Holdings Ltd. gained 2.3%.

A key gauge of bitcoin mining activity, the hashrate, has recovered from a steep plunge in early July, when China began a sweeping crackdown on the crypto industry. The hashrate measures the total computational power being applied on the Bitcoin blockchain to secure new data blocks on the distributed ledger.

The hashrate recovery has added to the positive investor sentiment for the miners.

“The bitcoin mining industry experienced the most dramatic short-term disruption in all history, with over 50% of the network hashpower coming offline throughout May,” according to an Oct. 4 report by analytics firm Glassnode. The report added that the Bitcoin hashrate has been on a “consistent path to recovery” since.

Meanwhile, the mining difficulty, a variable gauge that automatically adjusts under the Bitcoin blockchain’s code to keep the network running smoothly, has also been ramping up since the July slump.

“After bottoming out in late July, protocol mining difficulty has risen by 39%, with a further additional upwards adjustment of around 3.9% expected this week,” the Glassnode report said. Generally speaking, a higher mining difficulty tends to tamp down profits in the sector because new bitcoins become harder to find for the mining computers known as “rigs.”

MicroStrategy Inc., often seen as a proxy for bitcoin, climbed 4.3%, while crypto exchange Coinbase Global, Inc. gained 3% and Robinhood Markets, Inc., where many users trade crypto, rose 2.8%. The wider S&P 500 index and the Nasdaq composite were also in the green on Tuesday.

The gradual recovery in cryptocurrency prices over the past few months, combined with rising hashrate and network activity, suggests that mining firms could stay profitable even as the market remains volatile.

“Despite dramatic shifts in the mining market, multiple deep price corrections and a halving event in May 2020, the Bitcoin block reward value continues to rise, creating incentives for the market to adapt, innovate and recover,” Glassnode report said.