Kayleigh Wadsworth left her home in Selby, where she lives with her grandparents and her sister, following a family argument on Monday evening.
Police have set up an incident room and more than 50 police officers have been assigned to look into her disappearance.
Detectives started house-to-house inquiries on Wednesday morning.
Cowboy jacket
A spokesman for North Yorkshire police said the schoolgirl was last seen by her family at 1800 BST on Monday when she left her home in St John's Mews.
He said she was spotted by a friend at 2030 BST on Monday in Flaxley Road in Selby, but has not been seen since.
"The search will continue this morning with plain clothes officers visiting Kayleigh's friends and acquaintances, trying to gain any information which will help us," he said.
"There are 50 officers now involved in the inquiry and we are renewing our appeal for information."
The incident room has been set up in the town under the command of Deputy Chief Constable Peter Walker.
Kayleigh is 5ft 2ins tall with shoulder-length dark hair and has a missing front tooth.
She was wearing a distinctive denim cowboy jacket when she left.
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