In a letter sent on Tuesday to the U.S. Treasury Department and the White House led by Senators Elizabeth Warren, Roger Marshall and Representative Sean Casten, 105 lawmakers expressed “grave concern” that Hamas and an affiliated group called Palestinian Islamic Jihad were using digital assets to fund their operations and evade U.S. sanctions.

“Congress and this administration must take strong action to thoroughly address crypto illicit finance risks before it can be used to finance another tragedy,” the letter said.

Israeli police said in an Oct. 10 statement that it had frozen several crypto accounts that were used to solicit donations for Hamas. Reuters reported in May that Israel had seized around 190 crypto accounts at crypto exchange Binance since 2021, including dozens it said were owned by Palestinian firms connected to Hamas.

Binance said the exchange had been "working closely with international counter-terrorism authorities" on the seizures.

From its inception, the cryptocurrency community touted digital assets as vehicles for anonymous transactions, and a slew of federal enforcement actions for fraud, money laundering and unregistered coin offerings has put the industry in the spotlight.

Hamas uses a global financing network to funnel support from charities and friendly nations, including by using cryptocurrencies, Reuters reported on Monday.

Israeli authorities have seized “tens of millions of dollars” in crypto from Hamas-linked addresses in recent years, according to blockchain researchers TRM Labs.

The lawmakers requested that the Biden administration provide estimates on the value of crypto assets that remain in Hamas-controlled wallets, how much of Hamas’ operations are funded through crypto, and any information it has on the actors facilitating the sending of crypto to and from Hamas and other militant groups.