Three out of six lines were closed off at Malmö central station as the sweltering sun caused an expansion of the rails, a process that dramatically increases the risk of derailment.

“This entails certain delays but it won’t halt rail traffic,” said Jonas Bengtsson, spokesman for the Swedish Transport Administration.

Passengers on certain routes bound for Malmö were forced to either switch to different trains or take connecting buses in order to reach their destination.

Rail workers then had to wait until nightfall, and an attendant drop in temperatures, before being able to repair the rails.

Transport officials are on high alert and have already set aside resources to tackle the problem after Stockholm and Malmö each recorded two cases of thermal expansion on Monday.