The basement level of the station's shopping centre had to be evacuated and sniffer dogs were on hand in case it turned out to be a terror attack.
Several people in the McDonald's complained that they were having trouble breathing and were coughing at around 2pm, and people rushed to leave the fast food restaurant. Four people were taken to hospital with breathing difficulties.
When police searched the station they found an abandoned rucksack. "For security reasons, we of course checked it,” a police spokesman said.
The basement level of the train station was evacuated and closed and the tram service was stopped. An explosives expert who examined the contents of the rucksack found that it only contained sports clothes and gave the all clear.
At 3.30pm the station was reopened and the McDonald's was able to serve food again after the premises had been aired out and the food checked.
Police are examining CCTV material to find out who was responsible for the pepper spray.