Firefighters were called to attend a fire at an Elland nursery early on Friday morning.
The fire is reported to have been caused by an electrical fault and will render the nursery out of use for some time.
Engines from Rastrick, Halifax, Huddersfield and Cleckheaton were called out to the incident at 7.15am.
There was no-one inside the building and no-one has been hurt. Staff arriving at the building for work had notified the Fire Service of the blaze.
The fire itself was contained to the entrance hall of the building and has burned a hole through into the basement. The remaining rooms have been damaged by thick black smoke which has damaged toys and other contents and there is no indication of when the nursery will re-open.
Fire Investigation Officer Gary Kendrew said: “This is an accidental fire which we believe has been due to an electrical fault on the consumer unit.
“We believe the fire has been burning slowly for a number of hours, which would be necessary for a hole of this nature to burn through the floor into the basement.
“Sadly the other rooms within the building have also been badly damaged by smoke which is a good example of why we advise people to close internal doors at night, or when leaving a premises, to limit damage and spread should a fire break out.”