On Wednesday, Juneau became the fourth Alaskan city this week to receive a suspicious envelope containing a white powder substance addressed to the school district.

The unwanted correspondence sparked an evacuation of the Juneau School District’s Central Office, at the corner of 12th Street next to Harborview Elementary School, as the Capital City Fire and Rescue hazardous materials team, dressed in silver protective gear and orange boots, secured the area.

Similar letters were sent to the Tanana School District west of Fairbanks, Southeast Island School District in Thorne Bay on Prince of Wales Island and the Chugach School District in Anchorage, according to FBI Special Agent and spokesman Eric Gonzales.

“We have received four letters throughout the state these last couple days,” Gonzales said by phone from Anchorage.

The FBI is leading the investigation into the letters and is working with local and state law enforcement, fire departments, the postal service and public health, he said.

Gonzales said he could not discuss any leads in the case, but said substances in the other letters that had been tested for toxins have come back negative.

“To date, we haven’t had a positive, but that’s not to say that we’re not taking these letters very seriously and we’ve investigating it,” he said.

Gonzales said it appears that though the letters were all addressed to local school district offices, it appears they originated outside of Alaska.

“I don’t believe these letters are specific to Alaska,” he said. “I don’t think we’re being targeted. I think letters are just being sent nationally. Other communities are receiving these types of letters.”

Juneau School District spokeswoman Kristin Bartlett said she believed the letter was from Texas.

News outlets across the country reported on Wednesday suspicious envelopes, also containing a white powder substance and postmarked from Texas, were sent to five New England states: Massachusetts, New Hampshire, Rhode Island, Connecticut and Maine. The substance sent to one school district in Milford, Mass., turned out to be cornstarch, one news report said.

Capital City Fire and Rescue Chief Richard Etheridge said the substance would be sent to a lab in Anchorage for testing, and results could be back as early as this morning.

He said a school official alerted the fire department when she opened an envelope that contained the white powder substance around 12:45 p.m. Two members of the CCFR Hazmat team will be traveling to Thorne Bay, which is northwest of Ketchikan on the eastern side of Prince of Wales Island, help process the identical scene there.

Etheridge said all these precautionary measures have to be taken, and any type of hazardous materials incident has specific regulations to it.

“Most of the time it is a benign substance, but there is that off chance that it is a biological substance, so we have to have specific written operation plans,” he said.

• Contact reporter Emily Russo Miller at 523-2263 or at emily.miller@juneauempire.com.