The North Medford High School gymnasium roof collapsed Tuesday morning amid a cloud of dust and loud cracking and rumbling sounds, rendering the building a likely total loss and prompting evacuation of students and staff, Medford School District officials said following the dramatic incident.

Classes were canceled for students Wednesday, according to district administration. The district and city officials need to “assess the safety of the perimeter around the gym and develop contingency plans if certain areas remain inaccessible,” a statement said. Athletics already have been relocated, including prep basketball to Oakdale Middle School, and PE classes are being moved outside.

The roof, weighed down with snow from last week’s snowstorm throughout Southern Oregon, imploded inward less than an hour after media outlets had been briefed on the condition of the roof, and during which district officials expressed hope that building trusses could be shored up and damages repaired.

District Safety and Security Director Ron Havniear said an engineering team had been scheduled to assess damage to the gym and determine a course of action Wednesday morning. “At this point, this a full collapse and a tear down,” he said following the collapse.

“We’re just grateful that nobody was injured significantly, and that school is going to be able to go on.”

Havniear asked community members not to speculate on the cause of the collapse until a full assessment could be made.

“We’ll come up with a game plan and we’ll make sure the community knows that. We just ask for patience.”

A Facebook video of the collapse was posted by Tyler Myerly of the Medford School District.

Damage to the gym from a recent snow event first became evident when a crack appeared in a large wooden beam during a Friday evening sports practice. Students were evacuated, and the gym immediately fenced off to prevent access. Medford city, fire and engineering crews responded to assist in assessing the gym and help remove remaining snow load from the roof.

Havniear said the district estimated some 700,000 pounds of snow was piled atop the gymnasium roof.

On Tuesday morning, several beams broke loose and were hanging from the roof. The movement triggered alarms, prompting an emergency lockdown after emergency response buttons were activated at 8:41 a.m., the district said in an email Monday morning. The lockdown was lifted, but dispatchers reported at 11:26 a.m. that all students were being evacuated because of a “full collapse” at the gym.

During the media briefing, splintering sounds could still be heard above the gymnasium floor.

As seen in an overhead video, provided by the district, the roof collapsed as workers were working on site, prompting a second dispatch of emergency services just prior to 11 a.m.

While no injuries were initially reported, Havniear said one worker was in a rear doorway at the time the roof came down and was transported to a nearby hospital as a precaution.

“We were close to it, working on removing snow load on the roof and setting up a pump to remove water that was pooling,” he said. “We did have one person that was kind of in the doorway on the backside that was kind of blown out of that door and fell on the asphalt and kind of scraped up his knees. We transported him out of an abundance of precaution.”

Sophomores Laura and Benjamin Thompson, who are siblings, told the Rogue Valley Times on Tuesday morning that they were pulled into a lockdown drill immediately upon arriving at school Tuesday. Both said they were sad about the loss of the gym. Benjamin Thompson was in a building located adjacent to the gym and recalled a “loud rumbling sound.”

“I was in ‘S’ building, which is probably not more than 100 feet (from the gym). I heard a noise, but I didn’t know what it was until they started evacuating the building,” Benjamin Thompson said.

“I heard some staff saying that they think the rest of it might collapse even more, but I don’t know if they were talking about the rest of the roof or the whole building.”

Havniear said the building should be considered extremely dangerous to be near and that a wider perimeter will be fenced before students return to campus. A more than $3 million seismic retrofit of the structure over the summer, he noted, likely prevented the walls from collapsing with the roof. He pointed to steel reinforcements still attached to upright exterior walls after the collapse.

“This thing is built as a system, so once you start to see a portion of that system break down, then it just kind of domino effects out, and that’s what we saw this morning,” he said.

“The seismic upgrade that is in place did hold those walls up and is intact. We did not have any walls fall or explode outward, so we’re grateful that those upgrades were in place, and it was not for nothing that that work was done.”

In a district email sent Tuesday afternoon to “North Medford High families,” NMHS Principal Allen Barber thanked students, families and staff for their patience and support.

“We understand this has been a stressful day for our students, staff, and families. We are incredibly grateful to everyone who responded with care and professionalism. Thank you to our teachers and staff for keeping students calm and safe, our facilities team for their tireless efforts to prevent further damage, and our partners at the City of Medford and Medford Fire for their swift support,” the email stated.

A web link was provided for frequently asked questions and further updates.