Police are investigating after vandals defaced a Black Lives Matter mural in Chicago to read 'All Lives Matter.'

Authorities in Oak Park reported that the incident occurred overnight on July 7, into the following morning.

Artists had only painted the mural, which is nearly 100 feet in width, two weeks before the 'act of vandalism.'

The vandals covered up portions of the mural so that it read "All Lives Matter."

After the incident, community groups came out to wash the graffiti off the mural the next morning.

Local officials and artists who created the mural said they'll discuss whether it'll need additional work to restore it fully.

Oak Park Area Arts Council Executive Director Camille Wilson White told the Chicago Tribune:

"The public works department did a really good job of getting the [material] used to deface the mural up... It cleaned up really well."

"There are some areas that the artists eventually may want to look at restoring some of the paint."

One of the artists, Kasani Cannon, told Fox 32 Chicago:

"The movement lives within us. You can paint over it, you can drive over it... But once this mural dries, our movement still goes on."

"It's unfortunate. But I think it's good we get to see, in my opinion, the true colors of Oak Park."

Oak Park police have already gathered evidence. They now hope to identify the vandals.

The mural was the idea of Cullen Benson, a graduate of the local Oak Park and River Forest High School.

The sign reflects the colors of the LGBTQ+ Pride flag. It also has navy blue and orange for local high schools.

As per NBC Chicago, the mural is a 'testament to community acknowledgment of the Black Lives Matter movement.'

The BLM movement focuses public attention on the inequities and systemic racism that negatively impact people of color.

The Chicago sign is one of many Black Lives Matter murals authorities and activists have painted on sidewalks and roadways across the country following George Floyd's death.

In Washington, Mayor Muriel Bowser unveiled a large mural close to the White House.

Communities have also painted a giant Black Lives Matter mural on 5th Avenue, outside Trump Tower.

Despite the efforts to paint the murals, there has been some resistance to the signs. And the Oak Park mural isn't the first to be defaced.

In a similar incident, a California duo also defaced a Black Lives Matter mural outside Martinez's courthouse.

The pair rolled black paint over the bright yellow lettering, as they stated:

"There is no oppression. There is no racism. It's a leftist lie...from the media."

Police arrested and charged them with vandalism, violation of civil rights, and possession of tools to commit vandalism of graffiti.

If convicted, both defendants may face up to a year behind bars.