A hazmat team responded to a suspicious package full of powdery white substances at an Issaquah office building Thursday afternoon, after 3-5 people reported headaches and dizziness.

The team asked the 300-400 employees at the building to be sheltered on site until it could be determined if the substance was dangerous, said Eastside Fire and Rescue spokesperson Josie Williams.

Those who reported feeling sick began feeling better fairly quickly, she said. Although there were aid cars ready, no one was taken to the hospital.

The incident began at about 2:30 p.m., and the employees were released from the Lake Place II building, 1605 N.W. Sammamish Rd., by about 5:15 p.m.

Investigators have yet to determine what the substance was.

Issaquah Police, the FBI, and the U.S. Postal Service are jointly investigating the incident.

Bellevue police also responded to the scene.