LIVERMORE FALLS — As patches of flames spread along the wooded side of Route 133’s guardrail toward the Holy Cross Cemetery on Thursday night, Chrieten’s Greenhouse owner John Johnson found himself in a deja vu moment while he shoveled sand on the fire as the sun set.

“I got here I think, right as it first started,” Johnson said. “There were only two other people here, and I grabbed a shovel and went down over the hill where essentially, I fought it last time and then just kept trying to hold it until the trucks eventually got here.”

Chrieten’s Greenhouse is directly across the road from where the fire occurred, which seems to be a repeat spot.

Johnson also held off a grass fire from spreading in the same location just a month ago.

“This was a lot bigger than the last one,” he said. “The flames were as high as us, and plus it was dark so it appeared a lot more minatory. The heat was incredible,” he said in the entrance of a greenhouse overflowing with hanging flower baskets.

Forest Ranger Brad Bucknell was investigating the cause of the fire by photographing and analyzing the charred path and collecting witness, landowner and firefighter reports.

“They can tell us a lot about how the fire was spreading,” he said. “If they’re here early in the incident, that gives you a good indication of where the fire was early on and where it started. So we use that and after the fact, like right now, we’re looking for any type of object that could have started it and also burn patterns in the vegetation, and a lot of times those indicators point us in the right direction too.”

After following the burn path and finding small pieces of scattered metal, Bucknell was able to determine the cause was a passing vehicle’s broken catalytic converter.

“Catalytic converters have what looks like a sort of honeycomb matrix of metal inside them,” Bucknell said in a phone interview. “When they fail or when they break, essentially that matrix inside breaks into little pieces and it comes out of the exhaust red hot. We see fires quite often that are started by those pieces.”

This scattering of metal from the catalytic converter also explains why the fire occurred in patches alongside the road.

“It’s also common for them to cause multiple fires like that because you have all kinds of little pieces of red hot metal coming out of the exhaust, particularly if the vehicle is traveling at a pretty good rate of speed,” Bucknell said.