Denver police are investigating an incident in which someone used gasoline on Monday night to burn an anti-Semitic symbol on asphalt near the playground at Ellis Elementary School in the southeast part of the city, according to the school district.

“Hate will never be welcome in Denver Public Schools,” Superintendent Susana Cordova wrote in a letter Tuesday to families and district employees. (Read it below.) She added that she wanted “to take this opportunity to encourage all of us to stand united against hate. I want to encourage all of us to raise our voices in opposition to this action and all types of hate speech.”

Ellis Elementary Principal Nichole Whiteman said in a separate letter that she had notified the staff at the school about the incident but would not be making an announcement to students.

“We do not believe any student saw the hateful image,” she wrote in the letter, also on view below. “However, they may have seen police officers present at our school today.”

Bias motivated crime investigators are working with Denver Fire, the police department said. The incident was reported at 8:15 a.m. Tuesday. The investigation is ongoing.

Whiteman said the Ellis school psychologist, as well as psychologists and social workers on the district’s “crisis team,” would be available to help students address their feelings and concerns.

Cordova included a reference in her letter to a resolution passed by the Denver school board in 2017 that says “the district is committed to providing safe and welcoming spaces where all students are able to focus on their education,” regardless of a student’s immigration status, national origin, race, or religion. At the time, the resolution was meant to assure immigrant families that the district would not share information about their immigration status with federal authorities.

In 2016, anti-Semitic graffiti was spray-painted on a door and some playground equipment at Isabella Bird Community School in northeast Denver. Community members erased the graffiti and replaced it with paper hearts bearing messages of encouragement, peace, and love.