Two Illinois high school students were killed in a spring break sledding accident in Colorado, school officials said.

The male students were identified only by their ages, 17 and 18 years old. They were students at Prairie Central High School in Fairbury, Illinois, school administrators said.

They were riding in tandem down the half-pipe at Copper Mountain Ski Resort in Summit County when they launched themselves from a large snowbank at the bottom, the Summit County Sheriff’s Office said.

The accident at Copper Mountain, a resort less than 80 miles west of Denver, happened around 8:30 p.m. Sunday, ski area officials said.

Copper Mountain said in a statement that it has a «sledding area» but that the activity is prohibited in several areas.

The halfpipe closes at 4 p.m. each day, and the show is off-limits to sledding at all hours in any case, the resort said.

«Safety is the top priority at Copper Mountain, and we ask our guests to observe posted signs and warnings and not enter trails and closed areas,» he said. «Copper Mountain closes all lift and trail access at 4 p.m. daily, including the halfpipe, which was closed and cordoned off at the time of the incident.

They hit hard ice, the sheriff’s office said, according to an NBC affiliate. KUSA of Denver, and were pronounced dead at the scene.

The Summit County Coroner’s Office was expected to determine the cause of death.

Dustin Lyman, the resort’s president and general manager, said in a statement that «the entire Copper Mountain team is deeply saddened by this tragic incident.»