Multiple essential systems are currently inaccessible at the Canadian library
No evidence of exposure to the data stored in MongoDB Atlas cloud, it says
Report alleged Sellafield IT systems were attacked by hacking groups linked to Russia and China
IT systems and phone lines are down
Care centres are closed from California to Rhode Island
But 'most' services are designed to operate offline
Firm says the threat actor was 'sophisticated' and 'persistent'
Executives first said hack was 'Just a small breach'