A high school northeast of Denver was on lockdown after Commerce City police said they received a report of a bomb threat. A spokesperson for Commerce City police said no weapons or explosives were found and no one was injured, but later in the day, they said that two students were arrested for filing a false report of a bomb and an active shooter.

While searching the school for suspects, victims, or weapons, officers found "what appeared to be a blood trail" in several areas of the school, according to Commerce City police. They later also found two students who were "covered in what looked like fake blood- the same substance officers had encountered in parts of the building."

The students are minors but were not otherwise identified by police. They face charges of interference with staff or faculty of an educational facility, felony false report of explosives, and false report of an active shooter.

"For many, calls of this nature are their worst nightmare. Whether a first responder, a parent, a teacher or a student — most will never forget this day," Commerce City Police Chief Darrel Guadnola said. "The notion that this call may have been part of a prank is highly disturbing and pulled valuable law enforcement resources away from real emergencies in the Denver metro."

About 200 officers and agents from multiple agencies searched the school for about an hour-and-a-half with the help of dogs and bomb detection equipment.

The Commerce City Police Department originally notified the community just after 1 p.m. in a Facebook post. Students, parents, and others in the area should still expect a large police presence from departments across the Denver metro area. Officers and deputies from Commerce City, Arvada, Thornton, and Adams County were seen outside the school, along with several FBI agents.

Commerce City police spokesperson Joanna Small said in addition to the original call about the bomb threat, they received unconfirmed reports of other activity at the school, none of which appears to have happened.

"That hasn't turned out to be the case," she said of the bomb threat and additional reports. "We have not found anyone who's injured and all the students have been safe inside the building."

She went on to say they have not located any suspects or any of the 911 callers as of about 2:40 p.m.

Roberto Lopez was outside the school and said he was waiting to hear from his son.

"We're calling him; he's in there, and we don't know what's going on right now," he said. "He answered us (earlier) and says that he's OK, but right now he's not answering."

He said he's been hearing unconfirmed reports from other parents, but police have not confirmed anything about the incident yet.

Other parents and grandparents outside the school told CBS News Colorado that they were concerned and had not yet gotten information from police or school district officials.

At 4:30 p.m., the school district said in a news release that "families and the community received updates every 30 minutes during the incident."

School district officials said one student experienced an unrelated medical issue at the time and was taken to the hospital by ambulance as a precaution, but was later released to their parents.

After-school activities were cancelled on Wednesday, but classes are expected to resume on a normal schedule on Thursday, and additional counselors will be made available to students who wish to speak with one.

School district officials also addressed the unconfirmed rumors that swirled on social media during the lockdown in its statement.

"The district acknowledges that several social media posts shared by non-employees of Adams 14 contained inaccurate information, which understandably may have caused significant stress and concern for many families," the statement read. "Adams 14 encourages the public to avoid sharing unverified information on social media during incidents, as it can unintentionally increase fear and confusion for families, divert law enforcement resources and place additional strain on those working to protect students. The district will continue providing verified updates as they become available."

Adams City High School has about 1,500 students and is about 12 miles northeast of Denver.