A collision just before 6 a.m. this morning at 3rd and 22nd Street is still tying up traffic and slowing down Muni trains, according to Alert SF, which recommends avoiding the area. A police patrol car and a Muni T-line streetcar collided at the intersection at 5:45 a.m., injuring two police officers, a Muni passenger and the Muni driver.

Muni has set up a "bus bridge" to ferry people around the accident scene.

According to the Appeal, via the SFFD, the Muni vehicle broadsided the police car while traveling at low speed.

This is the first collision between a Muni car and an automobile since, oh, three weeks ago when an N-train hit a Prius in Cole Valley.

We'll update you as we learn more.