All heating has been lost at Royal Bolton Hospital, meaning new emergency and maternity patients are being sent elsewhere.
Bosses issued a statement on Saturday evening (December 4).
They said they were 'working hard' with the hospital's estates team to fix the heating system.
All new admittances via ambulance and to the hospital's maternity unit are being diverted.
A spokeswoman for Bolton NHS Foundation Trust said in a statement: "We are currently experiencing issues with our heating systems and unfortunately have lost all heating at Royal Bolton Hospital.
"As a result, we have had to divert any new admittances via ambulance and to our maternity unit. We are working hard with our estates team at iFM Bolton to restore heating at the hospital, and hope to be back up and running as soon as possible. We apologise for any inconvenience this has caused.
"Please bear with us whilst we work through these issues.
If you have an urgent care need, please contact NHS 111 who can help direct you to the most appropriate place to receive care."
