A package addressed to a controversial Arizona sheriff was turned over to a bomb squad after a postal inspector deemed it suspicious.
The item was addressed to Joe Arpaio, the tough-talking sheriff of Maricopa County. He's well-known for his hardline anti-immigration policies that have led to accusations of civil rights violations.
The sheriff's office said Flagstaff police X-rayed the package, determined it contained an explosive device and neutralized it Thursday night.
But a law enforcement official told CNN on Friday that it's not clear whether the package contained an explosive device. And it isn't known whether the item contained any bomb components. Another law enforcement official said the package had wires coming out of it.
U.S. Postal Inspector Andrew Rivas in Flagstaff, who screened the package Thursday, considered it suspicious enough to call a local police bomb squad and the FBI.
"We evacuated the post office, got all our employees to safety," Rivas told CNN affiliate KTVK.
Rivas said authorities have an idea of where the package may have come from, but declined to specify, citing the ongoing investigation.
The FBI also declined to release details.
"I can confirm the FBI is involved in the investigation," said FBI spokesman Manuel Johnson in Phoenix. "At this time the FBI is not commenting further due to the matter being ongoing."
The Bureau of Alcohol, Tobacco, Firearms and Explosives also is investigating, ATF spokesman Mike Campbell said.
Flagstaff is about 150 miles north of Phoenix, the seat of Maricopa County.
Arpaio has made national headlines for years with his unorthodox -- and often controversial -- style of justice.
He has housed thousands of inmates in tents and forced all inmates to wear pink underwear. He has boasted about feeding each inmate on less than $1 a day.
Arpaio's critics say he has a long history of launching bogus criminal investigations against political opponents and anyone else who gets in his way.
He was the subject of a civil lawsuit by the Justice Department alleging civil rights violations. According to the complaint, the sheriff's office has displayed a pattern of discrimination against Latinos that includes racial profiling, unlawful detention and searches, and unlawful targeting of Latinos during raids.
Arpaio has denied any discrimination, and one of his attorneys called the Justice Department investigation a "witch hunt."
His office website touts his "get tough" policies and says his chain gangs contribute thousands of dollars of free labor to the community. Male chain gangs, as well as the world's first-ever female and juvenile chain gangs, clean streets, paint over graffiti and bury the indigent in the county cemetery.
After winning his sixth term last November, the 80-year-old sheriff said he doesn't plan on leaving office anytime soon.
"For my critics out there, I'm going to say right now: In January, I'm signing up for 2016. So I'm not a lame duck," he told a crowd of cheering supporters.
CNN's Greg Morrison and Joe Sterling contributed to this report.