Approximately 50 customers and Apple employees were evacuated from a Swiss battery store after the battery of a device overheated and started emitting smoke.

While it wasn’t disclosed which device was using the faulty battery, local media Watson (via 9to5mac) reports that the emergency services quickly responded to a call from an Apple Store in Zurich at Bahnhofstrasse 77, as no less than seven people reportedly suffered minor injuries.

An Apple Store employee suffered burns when trying to remove the battery, and six other persons, either workers or members of the staff, needed medical care because of smoke inhalation.

Zurich police say the Apple Store staff responded well to the incident and the overheated battery was covered with sand to stop the fire and prevent smoke from being emitted inside the store. Specialists from the Zurich Forensic Institute have already picked up the battery for further investigation in order to determine the actual cause of the incident.

iPhone battery incidents

Apple hasn’t issued a statement on this but the company is most likely investigating the incident itself to figure out what exactly caused the battery to start emitting smoke.

Battery overheating has become a major concern for device manufacturers, and even though Samsung was the company most dramatically impacted by this issue due to the exploding Note 7 units, Apple is no stranger of devices catching on fire.

Several iPhone models burst into flames in the last couple of years but no widespread issue has been identified until now, with most incidents said to be happening due to physical damage to the device (as it’s the case of bending on the iPhone 6 Plus) or because of uncertified accessories like chargers and cables.

It’ll be interesting to find out, however, what device suffered the battery issue, especially because there’s no chance third-party chargers were being used in an Apple Store, so the incident could signal a bigger problem.