A father and two children reported suddenly taking ill and vomiting after leaving their apartment and stepping out into the communal stairs of their building in Upplands Väsby, north of Stockholm, on Wednesday morning.

Shortly thereafter, another man arrived at the scene and also threw up.

Police cordoned off the building and ordered residents to remain inside their apartments as a specialist team in hazmat suits were sent in to confirm the cause of the mystery illness.

The cordon was raised later on Wednesday after establishing that the reason for the illness was no more than a standard vomiting bug.

Earlier on Wednesday, police were called out to a second similar incident in the Kungsholmen area of central Stockholm, where a woman began to vomit in the stairs of her apartment building.

This also turned out to be benign.