IXONIA, Wis. (AP) _ A tour bus carrying residents of a retirement home collided head-on with a delivery van Tuesday, killing four people and injuring 19 others, authorities said. A firefighter was hurt fighting the flames.

Twenty-two people were aboard the bus, authorities said. The van, which carried only the driver and cleaning supplies, burst into flames during the accident on state Highway 16, 30 miles west of Milwaukee.

Fifteen people, including a firefighter, were admitted to area hospitals and six of those were in critical condition late Tuesday. Five other victims were treated and released.

``There was no one that was not injured in this accident,'' Jefferson County Sheriff's Capt. Kevin Stapleton said.

Both drivers and two women in their 80s were killed after being thrown from the bus, authorities said.

The windows of the blue and white bus were shattered and recliner bucket seats were tossed around. Fire Chief Bruce Degner said one person was apparently ejected from the bus. The other passengers were dazed.

``They were just sitting there wondering what happened,'' he said.

Mike Leslie, 21, a clerk at a nearby gas station, was driving on a highway behind the van and watched it turn left onto a county road. He was about to follow when he saw flames _ no van, just ``fire and black smoke.''

``And then through the flames came the bus and the bus slammed into the ditch,'' he said. ``I couldn't believe it. It was just so fast.

``If I would have turned, I would have been there, right behind the van.''

Leslie later helped take people off the bus. Some were unconscious and one elderly woman was in ``bad shape.''

``Her face was bleeding pretty bad from her nose,'' Leslie said. ``She said her back and stomach hurt.''

Kathy Lafler said her mother-in-law, who moved into the retirement home a few months ago, was being treated at a hospital for a broken ankle, collarbone and knee.

``She seems to be doing OK,'' Lafler said. ``She's mostly in shock right now.''

Zinzendorf Hall, a retirement home in Watertown, chartered the bus to take people to a horticultural conservatory in Milwaukee, said Kyran Clark, Marquardt Village's executive director. They were going to view Easter flowers.

The retirement village's chaplain was counseling residents at the hall.