NiceHash, which advised users to change online passwords after it halted operations on Wednesday, has provided few other details about the attack on its payment system.
"We ask for patience and understanding while we investigate the causes and find the appropriate solutions for the future of the service," it said on its website.
It was unclear whether customers faced any losses from the hack.
Slovenian police said they were looking into the hack, but declined to elaborate.
This article was provided by Reuters.