Updated: 11:20 p.m.

Rep. Raúl Grijalva’s Congressional office in Tucson, Ariz., was closed Thursday afternoon after an envelope containing a white powdery substance was discovered there, local news outlets reported.

The lawmaker was in a different Tucson office when the envelope was discovered, his spokesman, Adam Sarvana, told the Associated Press. Sarvana told the Arizona Daily Star that no one appeared ill, but further testing will be needed.

The substance, which was inside an envelope with swastikas on the front, had been taken to Phoenix for testing, an FBI spokesman told the AP. The envelope had been mailed to the office, TV news station KVOA reported.

Grijalva’s offices have previously been threatened. A window in his Yuma, Ariz., office was shattered in July, and a bullet was found inside. The month before, a Phoenix man accused of threatening to assault, kidnap and murder the lawmaker and his aides was indicted, the AP reported.

Grijalva, a Democrat, is running for re-election against Republican Ruth McClung in what his campaign characterizes as the closest of his career. The Democratic Congressional Campaign Committee has recently decided to put money into the race, spending $63,000 on an ad for the Congressional Progressive Caucus co-chairman, the DCCC reported.

Kyle Trygstad contributed to this report.