Leeds United have closed their Elland Road stadium "following reports of a security threat to the premises".
Police say "investigations are currently ongoing to establish the credibility of that threat".
Leeds said their "offices, ticket office, foundation offices and club shop at Elland Road will be closed until further notice on the advice of the police".
The Premier League club has sent staff home because of the incident.
"We apologise for any inconvenience and we will inform the public when normal service resumes," Leeds added.
It is thought the closure follows a threat posted on social media.
"Police were called to attend at Elland Road football stadium following reports of a security threat to the premises," said a West Yorkshire Police statement.
"Investigations are currently ongoing to establish the credibility of that threat."
They added they were alerted shortly before 22:00 GMT on Thursday.