RICHMOND -- A head-on collision in South Richmond has critically injured three people and left at least four others hurt, police said.

One woman was ejected from a Chevy Camaro and is in extremely critical condition, police said.

None of the victim's names, ages or hometowns were released.

The collision at South 37th Street at Stege Avenue, in a residential neighborhood one block south of the city's major thoroughfare, Cutting Boulevard, happened about 7:20 p.m., according to Richmond police Lt. Bisa French.

Police said a white Chevy Camaro was traveling south on South 37th Street when it collided head-on with a Chevy pickup truck heading north. Upon impact, the truck tipped over and all three men were injured, one critically.

Of the four people in the Camaro, two have critical injuries, police said. The others in both vehicles appear to have non-life threatening injuries. The speed limit on the street is 25 mph and excessive speed could be factor in the crash, police said.

"We do have some reports that the Camaro was traveling at a high rate of speed and we are investigating if alcohol was a factor,'' French said.

Because the collision involves more than five victims it is considered a "mass casualty" incident and will tax emergency services, hospitals, police and fire services in the city for several hours, police said.

Check back for updates.

Reach Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.