UPDATE 6:30 a.m. – A spokesperson for Minneapolis-St. Paul International Airport (MSP) says workers are now returning to the Federal Aviation Administration’s tower after smoke in the building caused employees to evacuate early Tuesday morning.

According to Jeff Lea, the MSP spokesperson, evacuation orders were lifted as of 6:24 a.m. Tuesday, and smoke has dissipated. Lea says the evacuation orders have been lifted.

Operations are also expected to return to normal soon.

Currently, the cause of the smoke hasn’t been determined.

Check back for updates.

A previous version of this report can be found below.

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INITIAL REPORT 6 a.m. – Multiple emergency vehicles can be seen outside the FAA Tower at Minneapolis-St. Paul International Airport Tuesday morning.

According to an airport spokesperson, fire crews from MSP and other agencies are investigating smoke in the building.

The spokesperson says the impact to aircraft operations “is likely but unclear right now.”

No other details were immediately provided.

Check back for updates in this developing story.