Someone set fire early Monday to a family’s 40-foot trailer parked along a west Petaluma road, destroying their household and personal belongings, according to a Rancho Adobe fire official.

The fire was on Magnolia Avenue near Thompson Lane. Firefighters were called at 5:11 a.m., Rancho Adobe fire Battalion Chief Herb Wandel said.

Firefighters determined the blaze appeared to be an arson and contacted Sonoma County sheriff’s deputies, Wandel said. He declined to release details of how the fire was set.

The old trailer had been parked along Magnolia Avenue for about a month, with permission from the property owner. It was due to be moved in the next few days, Wandel said.

No one was at the trailer when firefighters arrived. An investigation determined it belonged to people who’d been living at the nearby Sampson family property at Liberty Road and Skillman Lane. Late last year Sonoma County officials closed the property to inhabitants following a fire. The people owning the trailer had packed their goods inside and moved it from the compound to Magnolia Avenue alongside a field, Wandel said.

What didn’t burn had heat and smoke damage and Wandel estimated the loss at $15,000.

In early October a fire at the Sampson property started when a woman fell asleep while smoking, catching a trailer on fire. The flames moved toward the property’s main house and an off-duty firefighter and passerby ran inside, rescuing the property’s owner, Rose Sampson, 91. She was treated for smoke inhalation at Petaluma Valley Hospital. She died about one month later. Her son, Tony Sampson, 61, escaped without injuries.

Over the last several decades the Sampson family has had numerous run-ins with neighbors and authorities, including code enforcement issues, arrests and political battles.