Bihar Tourism minister Sunil Kumar Pintu said the website www.Bihartourism.Gov.In remained hacked from morning till 2:30 pm.
The hackers posted the threat to repeat Hyderabad-like blasts, besides message like 'Pakistan Zindabad', he said.
The website is maintained by Mumbai-based IT company Amatya Media.
The website was later restored and the company is trying to trace the hackers, Pintu said, adding the department would lodge an FIR against unknown cyber criminals in the case.
If the cyber crime wing gets any complain from the tourism department it would probe the incident, he added.