Prediction markets platform Polymarket was forced to halt trading on its international platform Thursday for nearly an hour because of what it said was a compromise of third-party software.

There were also unconfirmed reports from users on Polymarket’s Discord channel who said their wallets had been drained.

While Polymarket did not confirm that users had lost money, it said on X post “anyone who has been impacted will be made whole.”

“We’ll make this right and are fully reimbursing all affected traders,” the company said in a subsequent post on X.

Polymarket said the attack appeared to emanate from the United Kingdom and that it had referred the matter to British law enforcement authorities.

The hackers gained access to the funds via software from DebugBear, a web analytics and website performance tool, according to a person familiar with the details who was granted anonymity to address an evolving security situation.

DebugBear said on X that it was experiencing an “ongoing security incident” at around 2 p.m. ET Thursday.

Crypto news website The Block reported that some $2.65 million in cryptocurrencies had been siphoned from Polymarket users’ wallets, citing data from blockchain analysis group Arkham.

A Polymarket representative declined to comment on that figure or on the precise nature of the attack.

Polymarket said in its X post that it had identified and fixed an issue affecting its international platform, Polymarket.com.

“One of our 3rd party providers was compromised, and we have referred this to relevant law enforcement,” Polymarket said.

“Out of an abundance of caution, we have temporarily halted trading & are working to bring the platform back online,” it added.

Trading began again at 3 p.m. ET after nearly an hour offline.

Polymarket’s U.S.-based platform did not appear to be affected by the breach.

Compromising third-party vendors has become a common way malicious actors gain access to large platforms and websites.

These hackers’ success in stealing money from Polymarket users, however, makes this a significant breach.

Polymarket was valued at $21 billion in September after a group of investors led by Donald Trump Jr. invested $1 billion in the platform.

The company processes about $200 million worth of trading activity daily.

Polymarket, along with rival Kalshi, has become the subject of an intense, multimillion-dollar battle between U.S. states and the Trump administration over who gets to regulate the prediction-market betting that occurs on the sites.

The platforms also continue to fight off potential insider trading activity. Earlier Thursday, Bloomberg News reported Polymarket was investigating reports of suspicious bets made amid Israel’s closely watched elections.

It is also investigating “dozens” of bets related to the U.S. midterms, according to the company’s head of global intelligence and investigations, Shana Bautista.

Earlier this month, Kalshi said it was looking into suspicious bets involving Trump’s choice for press secretary.