Arson investigators are still assessing what caused an approximately half-acre fire that scorched part of the trails of the El Dorado Nature Center on Wednesday evening, keeping the facility closed on Thursday, officials announced today.

Police arrested Armando Vasquez Herrera Wednesday night on Katella Avenue near the 605 Freeway on suspicion of arson of forest land. He is being held on a $75,000 bail. Arrest records list Herrera as a transient.

“A possible encampment was involved,” LBFD spokesman Jake Heflin said.

Nature Center staff are still assessing the damage to the trails and it is so far unclear how long the center will be closed, Parks and Recreation spokeswoman Jane Grobaty said.