The powdery substance found in a suspicious package, which lead to the lockdown of a Costco building last week, turned out to be little more than cornstarch.

The common baking ingredient was used by a plastics company to keep samples from sticking together, said Issaquah Police Department Commander Scott Behrbaum.

Although the package was expected, the packing material was not.

Regardless of the results, the Costco Travel employees did the right thing when they received the package, he said. “In a similar case, we would encourage people to do what they did.”

When the group first opened the package in the afternoon Jan. 14, some employees complained of headaches.

“People are always worried about getting exposed to something,” he said. “If they know what they’re dealing with, they can handle it.”

The employees sealed the shipment in a bag and called police.

The Eastside Fire and Rescue hazmat team responded to the building at 1605 N.W. Sammamish Rd. at about 2:30 p.m.

The team asked the 300-400 employees to be sheltered on site until they could determine if the substance was dangerous. By about 5:15 p.m., the employees were free to go home, said ESFR 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.

Later testing by the hazmat team determined what exactly the substance was. The FBI and the United States Postal Service partnered with Issaquah Police in the investigation, and Bellevue police also responded to the scene.