JOHNSTOWN, Pa. - A truck sporting images and messages against slain civil rights leader Martin Luther King Jr. has drawn the attention of Pennsylvania authorities.

It was seen around Johnstown on the King holiday, featuring a sign extolling King assassin James Earl Ray, a Confederate flag, a dark stuffed animal hanging from a noose and a mannequin of a black man.

But the American Civil Liberties Union says the truck displays are protected free speech.

"He has a right to say those things," the ACLU said in a statement Tuesday. "The First Amendment gives you the right to say things that are obnoxious and wrong, and this is both."

Still, Johnstown police and the Cambria County district attorney's office are investigating whether charges of ethnic intimidation might be filed against the truck's owner, who hasn't been publicly identified.

At least one picture of the truck surfaced on Facebook after it was seen around Johnstown on Monday.

A sign on the truck's tailgate said, "In Loving Memory of James Earl Ray." A black mannequin's head hung over the tailgate on one side of the truck, with the stuffed animal hanging on the other side.

"We're actively working on this with the Johnstown Police Department ... to determine whether there is anything more to this than the photo," First Assistant District Attorney Heath Long said.

Among other things, investigators are trying to determine whether other incidents involving the driver might have crossed the line from free speech to criminal behaviour.

Interim police Chief Jeff Janciga called the image "in poor taste any time of the year" but even more so on the King holiday. But he reiterated that hateful speech is often protected, noting a Kansas church known nationwide for picketing the funerals of gays and others it opposes.

"Look at the Westboro Baptist Church and what they do at funerals," he said.

Alan Cashaw, who heads the local NAACP chapter, said the truck's imagery is hateful.

"If he wants to not like Dr. King, please find another way to display it," Cashaw said.

News from © The Associated Press, 2017