Cass County authorities have joined Park Rapids police investigating the similarities between firebombing incidents in both counties.
Last month a Molotov cocktail was thrown through a side window of Belle Taine Glass, off Highway 34 in Park Rapids.
The cocktail extinguished itself once inside the company's offices, but causes gasoline stains and window damage.
Two similar incidents occurred in Cass County, to Spitzack Builders in Walker, said Cass County investigator Robert Stein. One was in September 2008; the second March 24.
Although Spitzack Builders has worked on various projects with Belle Taine Glass, Stein said it is not known at this time if their work together is the subject of some type of retaliation or anger.
Stein said the types of firebombs were similar but are being analyzed.
"It's just a theory right now," said Park Rapids Police Chief Terry Eilers. "Until the BCA gets a chance to match the stuff up, there's enough similarities in the types of jars and that stuff" to believe the crimes may be linked.