No further hay arsons have occurred since a Washington county sheriff's office offered a reward and increased public attention.
Hundreds of thousands of dollars worth of hay was destroyed in at least 12 fires in the rural Quincy, Royal City and Ephrata areas from October to November.
Kyle Foreman, public information officer for the Grant County Sheriff's Office, said the case remains open and under investigation.
No suspects have been identified, but law enforcement and fire officials continue to work the case, Foreman said.
"The weather has reduced the risk, but also I think the public's awareness of the problem and more eyes, more people watching out for each other and for suspicious activity has also reduced the risk," Foreman told the Capital Press.
Farmers must always be vigilant, Foreman said
"It shouldn't just be when we start having issues and problems, we need to remain vigilant all the time to deter crimes in rural areas," he said.
Authorities at the time set a $15,000 reward for information leading to the conviction of the people who set the fires. The offer remains open, Foreman said.
People should call 9-11 to report suspicious activity. Foreman recommends descriptions of the people or vehicles involved.