A tornado destroyed an Alabama high school Thursday, trapping students under piles of debris and killing at least 20 people, including 15 at the high school.

Emergency crews dug through the rubble in the night, looking for survivors. The death toll fluctuated, but officials warned that more bodies could be found.

Rescue workers search for victims inside Enterprise High School in Enterprise, Ala., after a tornado ripped through the town on Thursday afternoon.
(Dothan Eagle, Danny Tindell/Associated Press)

"The number could very well increase as the search effort continues through the night," said state emergency management spokeswoman Yasamie Richardson.

The afternoon twister was part of a string of violent storms that rolled through the United States and Eastern Canada during the day, killing at least eight people in Alabama and one in Missouri.

Erin Garcia, 17, was inside the high school in the southern town of Enterprise, about 120 kilometres south of Montgomery, when the tornado struck at 1:15 p.m. CT and the school roof caved in.

"I was just sitting there praying the whole time," said the senior, who managed to escape unharmed.

"People didn't know where to go. They were trying to lead us out of the building. I kept seeing people with blood on their faces."

An overturned car and scattered debris are seen outside Enterprise High School.
(Dothan Eagle, Danny Tindell/Associated Press)

Enterprise High School and its stadium were destroyed, while trees around the building were uprooted and cars in the parking lot were blown over.

Emergency officials would not say whether the people found dead so far were students, teachers or both.

Martha Rodriquez, a 15-year-old sophomore, arrived at the school moments after the storm hit and found a scene of total destruction.

"It was just horrible," she said.

The school was right in the path of the storm, said meteorologist Paul Duval.

Homes in other parts of Enterprise, a town of 23,000, were damaged as well, and at least two people were killed.

More than 50 people went to the Enterprise hospital with storm-related injuries.

In Miller's Ferry, a rural community about 100 kilometres west of Montgomery, a storm tore through a trailer park, killing one person and damaging mobile homes.

A storm also killed a seven-year-old girl in Missouri.

The weather system has since moved through southern Ontario, dumping snow on Toronto and surrounding areas before moving towards Quebec and Atlantic Canada.

With files from the Associated Press