LOS ANGELES -- Three people are reportedly in critical condition after a shooting on Wednesday afternoon at Evergreen High School in Evergreen, a small community located 50 kilometers southwest of Denver, the US state of Colorado's capital.

The injured are being treated with gunshot wounds at CommonSpirit St. Anthony Hospital, spokesperson of the hospital Lindsay Radford said, adding that they do not believe there are any other victims.

In an email sent to parents and guardians, Jefferson County Public Schools officials said the shooting happened outside the school and the building was under lockdown.

Hundreds of police and law enforcement officers responded to the high school for the shooting, Jefferson County Sheriff's Office (JCSO) said on social media.

JCSO's spokesperson Jacki Kelley was quoted by The Denver Post as saying that the school is being cleared currently, and she could not confirm if any of those injured were believed to be the shooter.

Colorado Governor Jared Polis said in a statement that "students should be able to attend school safely and without fear across our state and nation." "We are all praying for the victims and the entire community," Polis said.