Ten Internal Revenue Service employees became ill on Friday after coming in contact with an envelope smelling of ammonia at the agency’s office in Kansas City, Mo., local and federal officials said.

The employees complained of nausea, diarrhea and vomiting, James Garrett, a deputy Kansas City fire chief, said in a phone interview. Lucy Martinez, a spokeswoman for the federal Department of Homeland Security, said seven people were hospitalized. Chief Garrett said the injuries were believed to be “not serious at all.”