PORTLAND – Police are searching for a silver car that may have been driven by someone who threw a chemical explosive at the Occupy Maine encampment in Lincoln Park early Sunday.

But acting Portland Police Chief Michael Sauschuck said investigators do not believe Occupy Maine was the suspects’ only target. Officers had responded to a disturbance behind City Hall at about 3 a.m. when they heard an explosion that sounded similar to the one that occurred in the park an hour later.

Federal investigators have been contacted, but as of Monday the incident did not appear to have violated any federal laws, police said.

Stephanie Wilburn of Portland, who was sitting near where the chemical mixture in a Gatorade bottle was tossed at 4 a.m. Sunday, said she was startled and briefly lost hearing in her left ear when the device exploded beneath a table about 10 feet away. Wilburn’s hearing returned, and police said no injuries were reported.

Occupy Maine protesters say the attack has left them anxious but still determined to seek changes in an economic system that they say rewards corporate power at the expense of working people and the unemployed.

“We are more motivated to keep doing what we’re doing,” Wilburn said. “They have heard us and we’re making a difference.”

The bomb was thrown into an area near the camp’s kitchen.

“There was no fire. … We had a good 20 feet of thick smoke rolling out from under the table,” Wilburn said. She and a friend who ran over to look at it breathed in fumes that smelled like ammonia, she said.

Sauschuck said the first blast appeared to come from southwest of City Hall, in the direction of Monument Square and possibly farther west, he said. Officers scoured the area but saw nothing suspicious.

Police interviewed four to six protesters who were awake at 4 a.m. when the device was lobbed over the wrought-iron fence separating Lincoln Park from Congress Street.

Police say they have leads, but Sauschuck would not say what evidence was collected.

People reported hearing a thud as something landed on the grass beneath a canopy covering signs and supplies. Minutes later, the device exploded as the chemicals inside built up enough pressure to rupture the plastic container, police said.

The city contacted federal authorities, including the Bureau of Alcohol, Tobacco, Firearms and Explosives and the U.S. Attorney for Maine.

The ATF said such devices do not violate federal law because they are less dangerous than more powerful explosives, such as dynamite or black powder, and don’t throw shrapnel as a pipe bomb would.

Police would have to determine the motive of the person who threw the device to decide whether civil rights or other federal charges are warranted. That would bring the U.S. Attorney’s Office into the investigation.

“We hope to make contact with a suspect down the road to see what their mindset is,” said Sauschuck. The state charge would most likely be criminal use of explosives.

Witnesses said a silver sedan, possibly a Toyota or Nissan, had been circling before the attack, its occupants shouting phrases such as “Get a job” and “You communist.” Witnesses told police they believe someone from that car threw the device. Anyone with information is asked to call police at 874-8575.

Shane Blodgett of Augusta was sleeping in his tent when the explosion woke him.

“I heard a sound which I thought was a gunshot,” he said. “I was in fear for my life. I thought someone was walking around with a gun. I didn’t dare poke my head out,” Blodgett said. He eventually went back to sleep.

The park is bounded by Pearl and Congress streets, Franklin Arterial and the Cumberland County courthouse. The tents and tables have been moved to the interior of the park since the incident, to be farther away from the surrounding streets.

Sauschuck said police will pay special attention to the area, but he noted that it already has more police traffic than most areas because officers coming or going from the police station garage often use Pearl Street.

The chemical bomb was one of the few clashes reported at the nationwide protests — other than those involving protesters and police.

In Albany last week, a man grabbed a protester’s sign and charged into the demonstrators. Police, who had been poised to move the protesters, instead apprehended the man and forced him to apologize, reports said.

By contrast, the relationship between Portland city officials, including police, and protesters has been civil, said John Branson, an attorney for Occupy Maine. He does not believe Sunday’s incident will dissuade protesters.

“Certainly this is a very determined group of people,” Branson said, noting they have maintained their occupation through poor weather. “This is obviously a lot more serious than rain and cold and certainly people are frightened, but I haven’t heard anybody say this is going to cause them to pack up and leave or no longer be associated with the movement.”

Staff Writer David Hench can be contacted at 791-6327 or at: [email protected]