BIRMINGHAM, Ala. (AP) - Emergency management officials in northern Alabama say houses have been destroyed by what they describe as a tornado.

There was no immediate word on any injuries Friday. But the Huntsville-Madison County Emergency Management Office says ambulances are responding to neighborhoods near Huntsville.

Thousands of Alabama schoolchildren are getting out of class early because the threat of tornadoes and other severe weather across the northern half of the state.

More than 20 school systems say they are dismissing classes early Friday because of the possibility of severe storms. Otherwise, the bad weather could hit around the time schools normally dismiss for the day, based on predictions from the National Weather Service.