Reports of Irish patient data posted online after a cyber attack on Ireland’s health service appear to be accurate, a government minister said, as the fallout from the hack continues.

A Financial Times report that some patient data has appeared on the so-called dark web “seems very credible and accurate,” communications minister Eamon Ryan told RTE Radio on Wednesday.

Ireland’s Health Service Executive has shut down most of its computer systems since last week, after a so-called ransomware attack. Emergency rooms are open but are very busy because of the hack’s impact and patients should expect significant delays, the health service said. Many x-ray appointments have been canceled.

The health service systems may have been penetrated “several days if not a week or two in advance” of the attack taking place, Ryan said. “This was well thought through in terms of huge resources put into planning and plotting and waiting, and then once within a network, taking time extracting data” he said.

A similar attack on the health ministry itself was caught “relatively early,” Ryan said.