DENVER (CBS4) – An accident on southbound Interstate 25 at Santa Fe Drive quickly caused traffic backups Thursday morning.

Police responded to an auto vs. pedestrian accident at approximately 5:45 a.m. The person hit has unknown serious bodily injuries.

The left two lanes of southbound I-25 were blocked off at Santa Fe Drive, and the right two lanes were open. Delays backed up to West Colfax Avenue as of 6:10 a.m.

By 6:35 a.m. all lanes of I-25 had reopened.