SAN DIEGO — California Highway Patrol Sgt. Brian Pennings joined FOX 5 Wednesday to discuss the dangers of raves that have been popping up beneath San Diego freeways.

“Partygoers are finding these secluded places, industrial parks and whatnot, underneath freeway overcrossings and remote locations, and they’re putting up these impromptu gatherings,” Pennings said.

Three major raves were held in the San Diego area this summer, Pennings said. These parties are attended by hundreds to thousands of people, Pennings said, adding that the largest one he has seen consisted of 2,500 partygoers.

Pennings says these raves are dangerous because they’re often held in areas not meant for pedestrians, such as construction zones or riverbeds. These areas are dark, and the alcohol and drug use makes the activity even more unsafe.

“We had one here locally underneath the 805 where they had literally full access up the path to the center divide of the freeway between the two sides of the freeway,” Pennings said.

Pennings said the events are dangerous not only to the partygoers, but to drivers on the roadways.

“Not only are we dealing with the pedestrians potentially near the roadway that are potentially under the influence, but they are leaving from these locations potentially under the influence as well,” he added.

On top of partygoers using alcohol — some underage — or illegal drugs, they are also trespassing, committing vandalism and littering, Pennings said.

“It can range anywhere from a citation to an in-custody arrest depending on the severity of the violation,” Pennings said.