Authorities have opened a hate crime investigation after a synagogue in downtown Chicago was vandalized early Saturday, according to police.

Around 12:20 a.m., officers responded to a call at 16 S. Clark St. in the city's Loop, police said. [[412774103, C]]

There they found that the front window of the Chicago Loop Synagogue had been broken and "derogatory stickers" were posted on the entrance.

Evidence technicians could be seen removing two swastika stickers from the front door. [[412774313, C]]

Lee Zoldan, president of the the Chicago Loop Synagogue, said construction workers across the street witnessed the incident.

A black SUV pulled up, witnesses told Zoldan, and a passenger got out of the vehicle and used an object resembling a hammer or ax to break the window.

The person then went back to the car and retrieved the swastika stickers to put on the door. [[412778243, C]]

Saturday is the synagogue's Sabbath, Zoldan said, and services continued as usual beginning at 9:30 a.m.

The synagogue has not received any further threats, she added, though the board will discuss what further security measures they will take in the future.

The American Jewish Committee, a national advocacy group, condemned the vandalism in a statement Saturday, saying it came amid a rise in incidents of anti-Semitism across the country.

"The Chicago Jewish community will not be intimidated by anti-Semitic attacks on a house of worship," AJC Chicago director Amy Stoken said.

"The right of all religious groups to practice their faith without fear is a fundamental American value. Chicagoans must speak together clearly that the hatred behind this destructive behavior will never be accepted," she added.

Cardinal Blase Cupich, Archbishop of Chicago, weighed in on the incident Saturday as well. [[412784883, C]]

"We stand with our Jewish brothers and sisters as they worship at Chicago Loop Synagogue this Sabbath. Hate will not prevail. #NeverAgain," Cupich tweeted.

The Council on American-Islamic-Relations Chicago also denounced the vandalism, calling it "a shameful act of cowardice and hate."

"Chicago's Muslim community stands in full solidarity with our Jewish brothers and sisters as they deal with the trauma of this vile act of hate," CAIR-Chicago Executive Director Ahmed Rehab said in a statement."No American should have to feel vulnerable and at risk simply due to their religious affiliation."

"Unfortunately, we know the feeling all too well as mosque vandalism and burning has spiked recently in the US," Rehab's statement continued. "We recognize the source of hate as one, and regardless of religious affiliation, we stand together in solidarity against it as one. An attack on any is an attack on us all."

No one is in custody, and authorities continue to investigate.