Peoria police determined a bomb threat was credible, explaining an explosive device was found near an ethanol plant.

An evacuation order was lifted for the area surrounding a west-central Illinois ethanol plant on Saturday, hours after a bomb was found.

Peoria Police Chief Brad Dixon said officers were alerted to a suspicious package Friday afternoon at BioUrja Renewables. Bomb squad technicians rendered the device safe several hours later. After authorities determined the threat was credible, police said the evacuation of neighborhoods within a one-mile radius of the site would remain in effect Saturday.

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At around 1 p.m. on Saturday, authorities said no new devices were located, and the evacuation of a one-mile blast radius of the plant was lifted.

Ryan Presley, special agent in charge of the FBI’s Springfield office, pledged that investigators would work “tirelessly” to identify whoever was responsible and “bring them to justice.”

Earlier, Peoria Mayor Rita Ali confirmed that a bomb had been found.

“A device has been identified. We know it’s a credible threat. We know it’s a bomb,” Ali said. The mayor cautioned that “we don’t know if there are other devices.”

Ali told WMBD-TV on Friday that BioUrja is “a plant that has ethanol and highly combustible types of chemicals, and so that’s what alarms us.”

It’s not unusual for law enforcement agencies to receive bomb threats or reports of suspicious packages, though such calls often do not result in the discovery of an actual explosive device. Still, authorities take the reports seriously and must assess and investigate each potential threat.

Just earlier this week, hundreds of airline passengers in Europe had flights diverted or received military escorts following a series of bomb threats that officials have since said were malicious hoaxes.