Two major accidents are impacting traffic in downtown Denver on Thursday.

The left two lanes of southbound Interstate 25 are closed at Speer Boulevard in Denver because of an accident, the Colorado Department of Transportation reports.

A three-car accident with injuries 20 minutes earlier closed all lanes of southbound I-25 at Alameda Avenue. The ramp from eastbound 6th Avenue to southbound I-25 is also closed. Traffic is being diverted onto 6th Avenue, police said.

Serious injuries are still being assessed from the second accident, police said.

Alternate routes are advised.