Helsinki police on Friday evening shut down and emptied Torni hotel's Ateljee Bar after a woman allegedly dispersed an "unknown substance" in the establishment, the authority announced in a statement on Monday.

Police ordered the establishment to be shut down and sealed off after three workers suffered unspecified symptoms following the incident.

Authorities are awaiting test results of the unknown material from a forensic laboratory, Detective Inspector Crista Granroth told news agency STT.

Granroth did not take a position on whether the substance was spread in a liquid or gaseous form.

Police suspect the female customer intentionally dispersed the substance. However, Granroth said that authorities have not yet reached the woman.

There were several customers in the bar at the time of the incident, but Granroth said police have not received reports of others developing symptoms, however she added that it could be possible.

Police are investigating the incident as aggravated assault, endangering health and safety and damage to property offences.

Granroth said the possible aggravated assault charge was due to the act possibly causing a life-threatening injury.

The Ateljee Bar sits atop the 14-storey Torni Hotel in downtown Helsinki. After it was built in 1931, for a few decades it remained the tallest building in Finland.