MoneyGram has blamed a "cybersecurity issue" for an outage that has left users unable to send money for several days.
On Saturday, the company confirmed on social media that it was "experiencing a network outage impacting connectivity to a number of our systems".
By Monday, the remittance giant confirmed that it had "identified a cybersecurity issue affecting certain of our systems".
MoneyGram is the world's second-largest money transfer operator, with more than 50 million users who send more than $200 billion a year.
The company took systems offline in response to the cybersecurity issue and is working with external cybersecurity experts and coordinating with law enforcement.
In an update on Tuesday, it said: "We continue to make progress in successfully restoring some of our key transactional systems. Our dedicated team is actively working around the clock on resuming normal business operations.
However, it has not provided any indication of when services will resume, saying only: "Once all systems are fully operational, transactions that are currently pending will be made available to customers."