The fire, which investigators believe was set intentionally, damaged or destroyed more than a dozen trucks and trailers at Harris Ranch shortly before 4am Sunday.
In an email sent to media outlets including CBS47, the North American Animal Liberation Press Office said it had received an anonymous five-paragraph message that included several possible details about Sunday's fire.
"Containers of accelerant were placed beneath a row of 14 trucks with 4 digital timers used to light 4 of the containers and kerosene-soaked rope carrying the fire to the other containers," the message said.
The North American Animal Liberation Press Office does not participate in illegal activity but distributes messages from those who sometimes do, group spokeswoman said.
"This is more than just an act of arson. This is. There's a political reason behind their actions," said spokeswoman Nicoal Sheen, who spoke by phone with CBS47.
Harris Ranch was back open for business on Monday, company leaders said. It's the largest cattle feeding operation in California.
The anonymous message's author said they knew Sunday's fire would not force the ranch to shut down.
"We were extremely pleased to see all 14 trucks 'were a total loss.' " the message said.
"This could be a one-time action. This could be, you know, we don't know these individuals. We don't know when they'll strike. We don't want to know. All we know is we receive the communique and report on them," Sheen said.
Investigators with the Fresno County Sheriff's Office declined to comment about the anonymous message but told CBS47 that they were aware of it.
A spokeswoman for the Central California SPCA, which works to prevent cruelty to animals, says her organization does not support or condone the message author's actions.
"We much prefer the legal method of handling things. Going through legislature, working through groups that can combine all together to make needed changes so that animals can be treated humanely," said Beth Caffrey, Central California SPCA.
Harris Ranch declined CBS47's request for an on-camera interview. But company spokesman Mike Casey said, "The incident is still under investigation. We don't comment on rumors or unfounded statements from others."
Harris Ranch employees were scheduled to meet with insurance adjustors on Tuesday afternoon to try to determine how much damage Sunday's fire caused, Casey said.