A large fire which destroyed part of the main building at a college in Swansea was accidental.
About 100 firefighters tackled the blaze at Gower College on Tycoch Road, Sketty, which broke out just before 04:30 BST on Friday.
Mid and West Wales Fire Service confirmed the fire was not deliberate but would not give any more details.
The college said the fire started in the library on the third floor and spread to the fourth.
Lower floors have also been damaged by water used to put out the flames.
A college spokeswoman said: "The college was given the news from its structural engineers that the building has remained structurally sound.
"This enabled us to start pulling together a recovery team. The IT team is also working to get services up and running as soon as possible.
"The college is continuing to work with multi agencies including the fire service, police and insurers."
The college has confirmed the campus will remain closed to the 2,000 students returning from the half-term break on Monday and Tuesday.
However, those due to sit GCSE exams on those days will still take them at Hill House.
The fire service has also praised the college for keeping its fire doors closed.
"Although the fire was significant... the situation could have been a whole lot worse had the fire doors not have been closed," said deputy chief fire officer Mick Crennell.
"I would urge everyone to keep their fire doors closed, they really are there for a reason and they really do work."