Arsonists torched a supermarket while night staff were working inside.
Detectives said two people started a fire at the Tesco store in Hemsworth during the early hours of Saturday .
The suspects, believed to be aged between 16 and 18, broke into the front of the building, on Market Street, before starting a fire in the entrance, police said.
Detective Sergeant Mick Casey of Wakefield District CID, said: “Enquiries are ongoing with the fire service into the cause of this fire which is being treated as arson and which has caused damage to the supermarket entrance.
"We are keen to speak to anyone who has information about the fire or who saw a juvenile male and female outside the store just prior to the fire being started or walking away from it in the aftermath of the blaze to contact Wakefield District CID."
The incident took place sometime between 2am and 2.20am on Saturday, February 10.
Firefighters from South Kirkby and Featherstone stations attended the blaze.
Neil Hawkins, of South Kirkby station, said night staff were working in the supermarket at the time.
He said an alarm was activated and there was a full evacuation and that the store was closed for several hours.
The suspects were a male and female, both of average height and build.
The girl wore glasses and had her hair in a ponytail and the male had short hair.
A Tesco spokesperson said: "We're very glad that no-one was hurt in the fire and thank the emergency services for their response. We will be assisting them with their investigation."
Anyone with any information should contact police on 101 referencing crime number 13180068268.
Information can also be given to the independent Crimestoppers charity anonymously on 0800 555 111.