About 50 workers evacuated a United Airlines building at Honolulu Airport yesterday morning because of a sulfurous smell, shortly after emergency medical personnel were called to treat a woman complaining of chest pains.

The female employee was taken by ambulance to a Honolulu hospital and her condition was unknown, according to the state Department of Transportation.

Although some of the evacuated workers complained about the smell, about 100 other workers remained in the building, the department said, adding that it did not know if the woman’s problem was linked to the smell.

Airport fire officials checked the building but were unable to detect any chemical readings, and the odor apparently dissipated, the department said.

The building includes a call center where employees process reservations.

A possible cause was cooking by some workers inside the building, the department said.

Employees returned to the building at 11:15 a.m., about 35 minutes after the evacuation.

Ryan Markham, a state Hawaii Occupational Safety & Health Division employee, said the department had received several complaints about the smell in the past, but found nothing after conducting a couple of air-monitoring tests.

Markham said an inspector was planning to conduct an investigation yesterday afternoon, including more air-monitoring tests.

The investigation followed calls from the Honolulu Star-Advertiser about the incident — United Airlines did not report it, Markham said, adding that labor rules do not require businesses to report all work-place injuries.

Markham said businesses must report incidents under certain conditions, including the injury of three or more people or serious, catastrophic accidents.

United Airlines spokeswoman Sarah Massier said the airlines takes employee health and safety seriously.

"We immediately tested the building and confirmed that it was safe," Massier said.