Emergency crews treated at least 10 people due to a suspicious package found at the IRS building near downtown Kansas City Friday morning.

Fire officials said at this point, they still don’t know what made everyone sick.

"We have complaints of nausea, headaches, they are vomiting, some other symptoms as well," said KCFD Deputy Chief James Garrett.

As for the package, Garrett said it did not contain a substance like a powder, saying something airborne made workers sick.

"It has an odor that at least 10 people have succumbed to,” he said.

HAZMAT crews swarmed the building.

Garrett said it was not evacuated because the incident was confined to the mail room.

Several people were taken to the hospital by ambulances, some on stretchers.

"It came through the mail room. At least 10 people came in contact with it,” Garrett said. “It was a suspicious odor, like an ammonia odor. People had nausea and vomiting, the things that would be associated with ammonia."

The entire situation has some people upset.

On Facebook, one worker reached out to us and wrote, "I'm at the IRS working right by this. We found out from outside sources before management told us."

KCPD said this is a fire department investigation.

We reached out to the IRS for a comment. They have not responded.