A brush fire that broke out Friday in the Santa Ana River bottom in Riverside scorched two acres in heavy vegetation and prompted the arrest of a combative transient detained in the immediate vicinity of the blaze.

The non-injury brusher was reported just after 1 p.m. Friday near the Mission Inn Avenue bridge, west of Carlson Dog Park and north of Mt. Rubidoux, according to the Riverside Fire Department.

The agency said that multiple engine crews from the city, Corona Fire Department and Cal Fire were sent to the location and encountered flames moving at a slow rate through thick brush, complicating access.

A Cal Fire water-dropping helicopter was summoned to make drops on the blaze, which did not threaten homes or other structures.

A municipal arson investigator looking for parties who were spotted fleeing the fire's point of origin confronted a transient along a bike path where crews were deploying and attempted to detain him. The suspect, whose identity was not released, became hostile and reportedly tried to break a window on the investigator's city-owned SUV. The man was wrestled to the ground by the investigator and another firefighter, then handcuffed, according to reports from the scene.

Riverside police spokesman Officer Ryan Railsback confirmed to City News Service that patrol officers went to the location and took the individual into custody. There were no reports of injuries, though the man was taken to Riverside Community Hospital for medical evaluation.

The fire's forward rate of spread was stopped at 1:55 p.m., and full containment was expected by 5 p.m.

No road closures were in effect.

The dry river bottom is strewn with homeless encampments, mostly between Jurupa Valley and Riverside, and cooking, warming, debris and other fires are common year-round.