TAMPA — A small fire inside a fertilizer tank Thursday morning at the Port of Tampa produced a cloud of toxic gas that wafted over portions of Harbour Island and downtown, leading authorities to order people to seek shelter.

The fire began before 9 a.m. inside a tank that held solid sulphur just north of McClosky and Maritime boulevards. A company performing what fire officials described as "routine maintenance" accidentally sparked the blaze. A hole in the top of the tank produced a smoke plume that was visible on Harbour Island, where residents phoned 911.

Firefighters arrived a short time later and tried to extinguish the fire using steam, authorities said. But that only created more problems as the steam mixed with the sulphur to create a cloud of sulphur dioxide that rode the wind toward downtown and Harbour Island.

Sulphur dioxide is a chemical agent known to cause irritation of the skin, eyes and respiratory tract as well as headaches and dizziness. Tampa police issued an alert just after 10:30 a.m. urging people in the area to "shelter in place."

"For their safety, we wanted to make sure that they stayed inside," said Tampa Fire Rescue Capt. Lonnie Benniefield.

At least one resident of Harbour Island phoned rescue personnel complaining of skin irritation and watery eyes from the fumes, fire officials said. But no one was taken to the hospital.

Firefighters used a water mist to disperse the chemical from the air. At 11:15 a.m., police lifted the order to seek shelter.

The port remained open throughout the incident.