Photo via Twitter/PaloAltoFire

On Thursday night, at least 12 people were taken to the hospital with respiratory issues related to a mysterious odor at The Westin Palo Alto in California.

According to NBC Bay Area, Palo Alto and Mountain View hazmat and fire crews responded to a report of a suspicious smell at the hotel around 10:30 p.m. local time. Officials requested that all guests at the facility shelter in place.

Authorities on the scene confirmed that eight people were transported to Stanford Medical Center after being exposed to the odor. Another four victims were taken to El Camino Hospital in Mountain View, NBC said.

In a follow-up report from KRON4.com, investigators revealed that they could not find the source of the irritant, claiming that it most likely vented out and dissipated from the parking garage they were investigating.

The scene was cleared shortly after midnight, and the guests who were forced to wait in order to check in or leave the building were once again permitted to come and go. The official Twitter account of the Palo Alto Fire Department shared a recap of the incident:

Haz Mat incident is under control, crews being released. Unable to determine source of irritant, but believe it vented & dissipated

— PaloAltoFire (@PaloAltoFire) October 30, 2015

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