BOULDER, Colo. (CBS4)– The FBI and the U.S. Postal Service have joined in the investigation after a threatening letter was sent to a Jewish center with a harmless white powder inside and two suspicious packages were found nearby. Another Jewish organization also received a letter with harmless white powder in South Boulder.

“Why Boulder? Why here? I don’t know,” said Boulder Sheriff Commander Jeff Hendry.

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The events started when employees at the Jewish Community Center, located on the 3800 block of Kalmia Avenue, opened an envelope at 8:30 a.m. Monday. The envelope contained white powder and a letter that read, “You have enemies.”

(credit: CBS)

(credit: CBS)

There were about a dozen preschool children in the building at the time, along with staff. Worried parents gathered outside the center as a suspicious package was removed by robots.

“Kids are learning and then something like this happens,” said Hendry. “Three, four, five years old that parents had left at school. It’s hard.”

(credit: CBS)

(credit: CBS)

The Boulder County Health Department and a hazmat team responded to the incident, and an office where the letter was opened was isolated and the two employees kept safe. Everyone else was evacuated.

Sheriff’s officials said that while they were searching the area two packages were found and they were called suspicious. A bomb squad was called in to investigate.

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Less than three hours later the white powder was determined to be non-toxic. About the same time another envelope containing white powder was discovered at the Congregation Har HaShem in South Boulder.

Congregation Har HaShem in Boulder (credit: CBS)

Congregation Har HaShem in Boulder (credit: CBS)

Employees there were already on alert.

“When they heard about the package that was received at the J.C.C. earlier they decided to look through the mail outside and that’s when they found the suspicious package,” said Rabbi Mark Glickman.

That powder was also found to be harmless.

Investigators said both envelopes had return addresses on them but won’t comment on specific details of the investigation.

The FBI and Postal Service have joined the investigation. Federal charges may follow.

Rabbi Glickman said the tight-knit Boulder Jewish community is shaken but nothing will take the focus off the sacred holiday of Passover.

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“To not let incidents like this distract us,” said Glickman.