"Terminal 2 is closed until further notice - police are investigating odd size luggage," the airport wrote on Twitter.
Terminal 2 is closed until further notice - police are investigating odd size luggage— Copenhagen Airport (@CPHAirports) September 12, 2017
Airport spokesman Morten Bro told AFP "there has been an incident", without elaborating.
Copenhagen police meanwhile tweeted: "Police working at Copenhagen Airport and terminal 2 is blocked off, which can lead to traffic problems. Time horizon unknown."
Politiet arbejder i Københavns Lufthavn og terminal 2 er afspærret, hvilket kan medføre trafikale problemer. Tidshorisont ukendt.— Københavns Politi (@KobenhavnPoliti) September 12, 2017
Terminal 2 is one of two main terminals at the airport, serving both international and domestic flights.
By 9:35am, the airport announced on Twitter that the terminal had been reopened.
UPDATE: The Police have now completed the operation at CPH and closures at Terminal 2 have been lifted. 1/2— Copenhagen Airport (@CPHAirports) September 12, 2017
The airport also tweeted that congestion and delays were still likely as a result of the temporary closure.
"We expect delays and cancellations as a result," Bro earlier told AFP.
"We are asking all passengers to follow instructions from the police and security."