But Walker's assistants had already been warned about the possibility of receiving such a letter and called building security instead of opening it.

Montana Gov. Judy Martz's office and part of that state's Capitol were evacuated Thursday when a match ignited and started burning paper, The Associated Press reported.

Governors' offices in Idaho and Nebraska also received the rigged letters. No one was injured in any of the states.

"We were notified by the National Governors Association of the potential of receiving such a letter," said Amanda Covington, Walker's spokeswoman. The warning gave governors a description of what the letter might look like.

When the letter arrived at the Utah Capitol on Thursday morning, Walker's office manager noticed it fit the description of the rigged letters and called the state Department of Public Safety, which handles security at the Capitol.

A Salt Lake City explosives team was called in, and technicians opened the envelope from the bottom to extract the device.

"There's a match in there along with some blank sheets of paper," said DPS spokesman Sgt. Wade Breur. A striking device was set up so the match would strike as the paper was unfolded, he said.

"It's just really rudimentary," he said.

The letters have an Ely, Nev., postmark and bear an inmate number, leading authorities to believe they may have originated at the maximum-security Ely State Prison, Breur said.

The letter sent to Walker was taken into evidence. The Utah Division of Homeland Security and U.S. postal inspectors were investigating, said Breur.

"They didn't have any type of threat of actual explosion," he said. "We can only speculate that the person was just trying to disrupt business."

aebroughton@sltrib.com