London‘s tallest skyscraper was evacuated on Thursday following reports of smoke in the building’s basement.

According to Twitter reports from the building’s management and the London Fire Brigade, the Shard was evacuated at around 10:30 am on Wednesday as the building’s fire alarms went off. Ambulances and at least ten fire trucks reported to the location as approximately 900 people exited the building.

Dozens of firefighters entered the building to investigate the cause of the smoke in the building’s basement and the London Fire Brigade sectioned off a 50 meter perimeter around the building. Despite the alarm, no signs of fire were discovered and the smoke began to dissipate later Thursday afternoon.

Workers were allowed back into the building after the smoke had cleared shortly before 3 pm.

Despite the false alarm, the smooth evacuation served as proof that the building’s evacuation procedures are sound. Workers in the building reported that the evacuation took around 30 minutes. No injuries were reported as a result of either the smoke or the evacuation. A London Fire Brigade station manager told the BBC that the evacuation, which could have impeded firefighter progress, was “quite a quick and easy process.”

In addition to being London’s tallest skyscraper, the Shard is also the tallest building in the European Union. The building was completed in 2012 and replaced an entire office block in the city’s London Bridge Quarter.

Image via London Fire Brigade