Dr. Brian Froelke got to Joplin, Mo., from St. Louis at 3 a.m. Monday to set up a makeshift hospital and help replace St. John's Regional Medical Center, which took a direct hit from Sunday's tornado and was completely unusable.

"A major trauma center being knocked out of commission is the worst level of potential (emergency) we are able to respond to," said Froelke, who is chief medical officer for the Missouri disaster medical team and an emergency physician at Barnes-Jewish Hospital. "The members have been deployed to many disasters, and this ranks up as one of the most severe they've seen in terms of the amount of devastation."

The disaster team in Joplin, about 40 doctors, nurses, pharmacists and support staff, is working in a 30-bed tent set up at a local business as a replacement emergency department on the city's eastern side. About one-third of the team traveled from the St. Louis area.

Another Joplin hospital, Freeman Health System, lost some power and communication and had to divert ambulances to hospitals in other parts of the state.

Froelke said they saw about 20 patients Monday, most with minor injuries, including lacerations and broken bones. Patients with more serious injuries were sent to hospitals in Springfield and Kansas City.

The 183 patients who were at St. John's hospital when the tornado hit were evacuated within 90 minutes and sent to other Mercy hospitals in the region. Sister hospital St. John's Mercy Medical Center in Creve Coeur did not receive any patients from Joplin but was on standby for assistance, a spokeswoman said.

At least six people were killed in the Joplin hospital, including five patients and an unidentified visitor, and multiple staff members were injured.

"I spent most of my life at that hospital," emergency room physician Dr. Jim Roscoe said, his voice cracking. "It's awful. I had two pregnant nurses who dove under gurneys. I had staff who showed up. They were hurt, but they worked all night long. It's a testimony to the human spirit."

Roscoe compared the carnage with what he saw in 1981 when he dealt with the collapse of a skywalk at the Hyatt Regency hotel in Kansas City, where 114 people were killed. He said it was also similar to the scene in Haiti last year when he went there to help after the earthquake.

The Missouri medical disaster team members will deploy to Joplin on three-day rotations. Froelke said the team's mobile medical unit, a 60-bed temporary hospital, will be set up soon as St. John's hospital undergoes repairs in the coming months. It will be the first time the mobile unit has been needed in the state.

Any medical personnel who are interested in helping out in Joplin can register at showmeresponse.org — which coordinates the efforts.

The Associated Press contributed to this report.