SPOKANE, Wash. — Spokane Police said Wednesday they are continuing to investigate a social media threat toward Lewis and Clark High School that was posted Saturday night.

Police said the investigation is a "top priority."

Officials said detectives are working with school and federal officials. Patrol officers are continuing to monitor the school.

Authorities said detectives and technical support staff have dedicated a significant number of hours looking for and analyzing evidence.

Spokane Public Schools said school began without disruption on Monday morning. Uniformed police officers were watching entrances and roaming the campus, while several SPS resource officers were also on campus.

The school remained on modified lockdown for most of Monday and additional security will remain in place until the situation is resolved, SPS said.

"We know this is a frustrating time for families and staff and we will provide updates as we are able during this active law enforcement investigation. Thank you for your patience and support," SPS wrote on Facebook Monday morning.

Spokane Public Schools initially sent an email to parents Sunday morning about the threat.

The full email reads:

Spokane Public Schools is working with the Spokane Police Department to investigate a threat made Saturday night via social media. SPD has assigned investigative resources that worked throughout the night. The investigation remains open and active, and SPS safety personnel are in continuous contact with law enforcement.

Language in the social media post makes threats again Lewis and Clark High School. Law enforcement is working to identify the source and determine the credibility of the threats.

Both SPS and law enforcement take these types of incidents and the safety of students and staff very seriously. Additional SPS resource officers and SPD officers will be at LC on Monday to ensure students and staff can attend school safely and uninterrupted.

We will provide additional updates as details become available, but want to make you aware of the situation even as the investigation is still very early and active. It is frustrating to be once again investigating this type of threat, but it is important that you know that law enforcement and SPS are doing everything it can to thoroughly investigate and quickly determine the source.