JOPLIN, Missouri (AP) -- A massive tornado that tore through the southwest Missouri city of Joplin killed at least 89 people, but authorities warned that the death toll could climb Monday as search and rescuers continued their work at sunrise.

City manager Mark Rohr announced the number of known dead at a pre-dawn news conference outside the wreckage of a hospital that took a direct hit from Sunday's storm. Rohr said the twister cut a path nearly six miles (ten kilometers) long and more than a half-mile wide through the center of town.

Much of the city's south side was leveled, with churches, schools, businesses and homes reduced to ruins.

Fire chief Mitch Randles estimated that 25 to 30 percent of the city was damaged, and said his own home was among the buildings destroyed as the twister swept through this city of about 50,000 people some 160 miles (255 kilometers) south of Kansas City.

``It cut the city in half,'' Randles said.

An unknown number of people were injured in the storm, and officials said patients were scattered to any nearby hospitals that could take them.

A door-to-door search of the damaged area was to begin Monday morning, but authorities were expected to move gingerly around downed power lines, jagged debris and a series of gas leaks that caused fires around the city overnight.

``We will recover and come back stronger than we are today,'' Rohr said defiantly of his city's future.

St. John's Regional Medical Center appeared to suffer a direct hit from a tornado. The staff had just a few moments' notice to hustle patients into hallways before the storm struck the multistory building, blowing out hundreds of windows and leaving the facility useless.

In the parking lot, a helicopter lay crushed on its side, its rotors torn apart and windows smashed. Nearby, a pile of cars lay crumpled into a single mass of twisted metal.

Triage centers and shelters were set up around the city.

Emergency management officials rushed heavy equipment to Joplin to help lift debris and clear the way for search and recovery operations. Missouri Gov. Jay Nixon declared a state of emergency, and President Barack Obama sent condolences to families of those who died in storms in Joplin and across the Midwest.

Jeff Lehr, a reporter for the Joplin Globe, said he was upstairs in his home when the storm hit but was able to make his way to a basement closet.

``There was a loud huffing noise, my windows started popping. I had to get downstairs, glass was flying. I opened a closet and pulled myself into it,'' he told The Associated Press. ``Then you could hear everything go. It tore the roof off my house, everybody's house. I came outside and there was nothing left.''

In Minneapolis, Minnesota, at least one person was killed and 30 others hurt. At least 100 homes were damaged, and a joint city-county team planned to be at the shelter Monday to begin assessing emergency housing needs.