A three-month investigation into a pot farm in a remote area north of Guerneville led to the arrest Saturday of four Sonoma County men and the discovery of about $150,000 in marijuana plants.

A state parks surveyor in May noticed what investigators called “suspicious” materials, including empty food containers, sleeping bags, lawn chairs and empty ammunition casings along the northern edge of the Austin Creek State Recreation Area — a sign of a possible pot grow, said Jeremy Stinson, a supervising ranger with California State Parks.

Stinson, along with nine other state park rangers and four Department of Fish and Wildlife wardens, concluded their investigation at about 8:30 a.m. Saturday, ultimately seizing 153 pot plants from the park, along with hundreds of feet of irrigation pipe and wire fence.

“The area is so remote, so it’s not a place that we can get to every day when we’re dealing with pot growers, especially when we know they’re armed,” Stinson said. “We set up our operation yesterday and arrested four of the five suspects.”

Stinson said five men parked a truck on a difficult-to-reach northern park slope, then walked down to their growing operation, which was lined with irrigation tubing and wrapped in wire fencing. Investigators announced themselves to two of the men, sending the three others back to the truck. One of the men threw a semiautomatic pistol from his waistband when confronted, then surrendered.

Rangers and other park officials detained four of the five men and concluded the investigation late Saturday afternoon, Stinson said. He said the men, identified as Alfredo Soto, 33, of Santa Rosa, Noe Calderon-Garcilazo, 32, of Santa Rosa, Jose Reynoso, 41, also of Santa Rosa and Erick Reynoso, 34, of Cotati were arrested and taken at about 4 p.m. Saturday to the Sonoma County Jail. All four were released on bail early Sunday morning, a county jail official said.

Stinson said these kinds of investigations are a priority, especially when considering public safety.

“Marijuana grows are a huge problem for California state parks, and for public land in general,” Stinson said. “This was a pretty small operation in comparison, but in this case we were concerned with public safety because we had information that the people involved in the grow were armed.”

Stinson said the truck, which was seized by parks officials and towed, contained shell casings for more than one weapon.

Saturday’s pot seizure comes nearly a decade after Sonoma County’s biggest pot grow was closed down in the same park. Parks officials, along with the Sonoma County Sheriff’s Department in July 2005 discovered 23,653 pot plants in the southern part of Austin Creek State Recreation Area.

“That was the largest public land grow we’d discovered in Sonoma County history,” Stinson said.

Officials found 100 pot plants growing along the Russian River last summer, which resulted in the arrest of two men. Another growing operation netting 2,300 plants was discovered in 2009 near Austin Creek, and about 1,000 plants were found in September 2007 near Fort Ross along the coast.