Three Nevada men have been questioned by investigators about vandalism in an environmentally fragile area of Death Valley National Park that may have killed one of the rarest fishes on earth, officials said Friday.

No arrests have been made in the April 30 intrusion while authorities continue to investigate what could be a federal crime, Nye County Sheriff's Sgt. David Boruchowitz said. He said evidence includes DNA and video recordings.

The men from Pahrump, Indian Springs and North Las Vegas may be held responsible for the death of at least one critically endangered Devils Hole pupfish, Boruchowitz said, along with conspiracy, trespassing and damage to habitat charges.

Boruchowitz said a sheriff's sergeant was able to identify an off-road vehicle seen in surveillance video and interview the owner in Pahrump. The other two men were contacted by telephone.

Investigators determined the three had been shooting rabbits in the area before they climbed a fence into Devils Hole, a protected sanctuary in Nevada just east of Death Valley National Park in California, Boruchowitz said.

Police say they fired at least 10 shotgun blasts in the preserve, hitting a motion sensor and shooting the locks off of two gates. The National Park Service said they left beer cans and vomit, and one man waded into Devils Hole, leaving his boxer shorts in the water.

Boruchowitz said two surveillance cameras and several signs also were damaged.

On Monday, one of the pupfish was found dead, the Park Service said, although it wasn't immediately clear if it was due to the intrusion.

Just 115 of the inch-long fish were found in a periodic count last month in their hot spring-fed pool, which is more than 400 feet deep in parts but less than 2 feet deep where they feed.

The Park Service offered a $5,000 reward for the arrest and conviction of the intruders, and the Center for Biological Diversity added another $10,000.

Biologists closely monitor the rare species, which numbered more than 500 in the 1970s.

A U.S. Supreme Court ruling in 1976 barred groundwater pumping for agricultural use near the site because of its impact on Devils Hole.