SALT LAKE CITY – Authorities announced Thursday that a shell from an illegal firework ignited the fire that destroyed Michael Dobbs’s world-famous pop bottle collection last week.

Police had received calls about people lighting fireworks in a construction lot behind the neighborhood on the night of the fire.

“We received four calls earlier that night about individuals using aerial fireworks on the lot,” said Officer Jane Calhoun of the SLC Police Department. “We have been unable to locate the individuals so far.”

The lot in question is owned by Todd Kessler. Kessler recently announced plans to build a small convenience store on the lot and is in the process of selecting a contractor.

“We didn’t think we would have to worry about a fence until we started digging,” said Kessler. “A fence will be up by tonight to prevent any more trespassing.”

“The shell from an aerial firework landed in a patch of dead grass next to the house,” said Chief George Choper of the SLC Fire Department. “Unfortunately, it ignited the grass and spread to the Dobbs residence.”

Michael Dobbs was unable to be reached for comment.