An investigation is underway Saturday after a woman was found dead off a popular trail in Altadena, officials said.

The body was discovered Friday evening inside a tent off a trail at the Cobb Estate, according to the Los Angeles County Sheriff’s Department. The agency said homicide detectives are investigating the death, the cause of which is still unknown.

Sheriff’s officials were first notified of a tent with a “foul smell” emanating from it, Deputy Erin Liu of the Sheriff’s Information Bureau said in a written statement. The tent was sitting along a dirt road leading to a water tank in Las Flores Canyon.

“The body appeared to be long decomposed and there was no sign of trauma or foul play,” Liu said. “The reason of the death is unknown.”

Jose Zarazua told KTLA he was hiking when he noticed a tent in the bushes.

He said after seeing a head, he immediately went home and called authorities.

Others hikers at the trail’s entrance on Saturday morning said they were shocked to hear about the discovery.

“We have never seen anything like that… This is a very popular trail with children and dogs and all kinds of people,” one hiker said.

Another said, “If this is something violent in nature, then of course it’s going to affect us coming here.”

A trail through the Cobb Estate, locally known as the “haunted forest,” leads to Echo Mountain in the Angeles National Forest. The lumber magnate Charles Cobb built a mansion on the property in 1918 before it was donated to the U.S. Forest Service in 1971.

KTLA’s Brian Day contributed to this report.