Emergency lighting had to be used at a Leeds hospital centre last night due to a power dip causing an "extraordinary issue".
The outage affected the Newsam Centre at Seacroft Hospital, which treats people for mental health problems.
Chief operating officer Joanna Forster Adams said: "The electricity at Newsam Centre went off at 4.15pm on Sunday evening.
"The building had emergency lighting only for about two and a half hours.
"The situation was explained to service users and our staff worked hard to make sure everyone was safe and secure throughout.
"We understand that there was a power dip across Leeds which caused an extraordinary issue with the Centre’s back up generator.
"We are now in discussion with Interserve, which maintains the building under a PFI agreement, and the National Grid to minimise the opportunity for this to happen