Police have evacuated guests and staff at the Macdonald Inchyra Hotel and Spa in Grangemouth, and cordoned off the entrance to its grounds.
Precise details of the situation are not yet known, though unconfirmed reports suggest there has been a major chemical leak connected with the spa’s swimming pool.
Chemicals are understood to have spread through the hotel's air conditioning unit before the alarm was raised at around 7:30pm.
Authorities have not yet confirmed details of any injuries.
Along with a heavy police presence, three fire engines, a support unit and an ambulance Specialist Operations Response Team are also on the scene.
Photos taken from the entrance to the hotel, on Grange Road, show guests sheltering in the back of ambulances and police vans.
One eyewitness said emergency workers are establishing a make-shift centre for guests.
Police Scotland has been contacted for comment.