LONDON - U.S. crypto firm Nomad has been hit by a $190 million theft, blockchain researchers said on Tuesday, the latest such heist to hit the digital asset sector this year.

Nomad said in a tweet that it was "aware of the incident" and was currently investigating, without giving further details or the value of the theft.

Crypto analytics firm PeckShield told Reuters $190 million worth of users' cryptocurrencies were stolen, including ether and the stablecoin USDC. Other blockchain researchers put the figure at over $150 million.

San Francisco-based Nomad is working with law enforcement and blockchain analysis firm TRM Labs "to trace stolen funds, identify recipient wallets, and coordinate the return of funds," the company said in a statement on Wednesday. It did not specify which law enforcement agencies it was working with.

Nomad, which last week raised $22 million from investors including major U.S. exchange Coinbase Global, makes software that connects different blockchains - the digital ledgers that underpin most cryptocurrencies.

The heist targeted Nomad's "bridge" - a tool which allows users to transfer tokens between blockchains.

Blockchain bridges have increasingly become the target of thefts, which have long plagued the crypto sector. Over $1 billion has been stolen from bridges so far in 2022, according to London-based blockchain analytics firm Elliptic.

In June, U.S. crypto firm Harmony said that thieves stole around $100 million worth of tokens from its Horizon bridge product.

In March, hackers stole around $615 million worth of cryptocurrency from Ronin Bridge, used to transfer crypto in and out of the game Axie Infinity. The United States linked North Korean hackers to the theft.

Nomad described itself as "security-first" business which would keep users' funds safe.

PeckShield said that a small proportion of the coins were moved to a so-called "mixer", which masks the trail of crypto transactions, while around $95 million was held in three other wallets.

(Reporting by Elizabeth Howcroft; Editing by Tom Wilson, Christina Fincher and Mike Harrison)