Ethereum Classic( ETC), the original version of Ethereum network, has recently witnessed an astonishing rise of its miner rewards recently amid abnormal transaction fees . The event comes just three days after the ETC 51% attacker returned $100,000 worth of tokens back to the crypto exchange Gate.io.

According to a report from TrustNodes, ETC miners were rewarded as much as 200 per block on January 13, rather than the normal reward of 4 ETC . Meanwhile, another explorer showed 424 ETC were given to a miner in block rewards. At press time, the miner rewards registered by ETC Block Explorer gastracker io. fall to 109 ETC.

What’s noteworthy is that the consensus rules like block rewards for the the proof-of-work (PoW)-based Ethereum Classic blockchain network have not been modified by the major miner. Therefore, the higher-than-normal miner rewards seems to be caused by a huge transaction fee.

China-based blockchain security firm PeckShield said on Monday that the ETC address0xb71ee6225ac2904b61941797781ad5cb9182371d initiated multiple transactions which cost transaction fees of 105 ETC , but the exact motive behind these transactions remains unknown.

Some crypto enthusiasts believe the 51% attackers— who are assumed to controls more than half of the ETC network’s mining power to alter transaction history and double-spend coins—are using high transaction fees to launder money.

The event arrives days after the 51% attackers returned a mere fraction of of ETC tokens which they stolen from a recent deep chain reorganization of the ETC blockchain to the crypto trading platform Gate.io on Jan. 10.

The exchange declared in a statement that they have received around $100,000 worth of tokens from the 51 percent attacker, but still did not know the reason why part of the funds have been returned.

“If the attacker didn’t run it for profit, he might be a white hacker who wanted to remind people the risks in blockchain consensus and hashing power security,”The exchange said.

On January 8, Gate.io confirmed the ETC 51% attack and identified nearly 40,000 ETC ( worth roughly $200,000 at the time) were transferred to the attacker’s address. In wake of the double-spend attack, the exchange has raised the ETC confirmation number to 4000 and launched a strict 51% detect for enhanced protection.

Despite network abnormities, the price of ETC remains relatively stable. The 18th largest crypto by market cap is traded at $4.26, down 5 percent in the past 24 hours, according to coinmarketcap.