The alarm was raised at 7am, when staff members at the airport just outside of Växjö received the letter, prompting an evacuation of the airport. Several flights were also cancelled.
Airport head Ulf Axelsson refused to go into details about the contents of the letter, but insisted that the threat was not explicit.
“One of our employees got [the letter], read it, and understood that it could be interpreted as as a bomb threat. The police had the same understanding,” he told the TT news agency.
A bomb squad from Skåne has been assigned the task of investigating the situation, with Axelsson predicting flights to be in the air again “some time after lunch”.
Police are taking the threat seriously, according to Percy Nilsson of the Kronoberg police.
“We decided to evacuate the airport, and search the area with dogs,” he told the TT news agency, and added that the police bomb group would take “at least the whole morning” to investigate the threat.
All morning flights to and from the airport have been cancelled.
Would-be travellers have been taken by bus to both Jönköping and Kalmar airports, each roughly 100 kilometres from Växjö.
Flights from 3pm and onwards were opened to passengers in the early afternoon.