A loud explosion Sunday night near the Morro Bay Power Plant set off a flood of 911 calls from residents who described hearing the blast and seeing a flash and smoke.

Morro Bay police ultimately attributed the 10:07 p.m. explosion to a high-powered, improvised illegal firework device in a dirt parking lot next to the plant at 1290 Embarcadero Road.

No suspects have been identified, and police are asking for help from anyone with information about the incident.

Morro Bay resident Louis Mastrangelo, who lives about one mile away, said he was at home “watching the Olympics on TV, and it sounded like the starburst-like pop of a firework. I heard it, and I said, ‘What the heck?’ ”

Some residents in the area described feeling the ground shake, police Sgt. Su Gomes said.

About 60 people called to report the incident, Gomes said.

She said the culprits used cardboard packaging formerly containing soda cans as a type of funnel to eject the explosives.

The suspected fireworks were similar to those from Fourth of July aerial shows and aren’t available to the general public for purchase, Gomes said.

The lot, adjacent to the submarine display on Embarcadero Road, is separated by a fence from the power plant stacks and is mostly empty with some boats parked inside.

Walls enclose most of the lot, and the sound apparently reverberated and traveled up the nearby hill to the surrounding neighborhood, Gomes said.

The power plant retired its operations this month, but the explosion didn’t affect the facility, according to police.

The county’s bomb task force also checked out the scene and found cardboard and paper remnants of the explosion.

No show of lights in the air was visible, only a flash, Gomes said, and the ground also shook, which was widely felt by many in the area.

“It really caused a lot of concern,” Gomes said. “I think a lot of people were really scared for their safety.”

A representative from PG&E also was contacted, but the company reported no problems or outages.

The investigation is ongoing. Anyone with information is asked to call police at 772-6225.