WASHINGTON — A tornado has partially collapsed a FedEx depot in Michigan, trapping 50 people inside, officials say.

The rare tornado hit the small town of Portage, eight miles (13km) south of Kalamazoo, on Tuesday evening.

Emergency officials are working to reach those inside, but have been hampered by downed power lines and debris.

Multiple buildings have been damaged by severe weather in the region, but there are no reports of injuries.

More than 32,600 people are without electricity, according to the PowerOutages.US website. Thousands more are under weather warnings.

The National Weather Service (NWS) has issued its first tornado emergency for Michigan, the highest alert level.

Taylor Koopman, of the Kalamazoo County Administrator's office, told MLive.com that 50 people were trapped in the partially destroyed FedEx facility.

Collapsed wires and debris must be removed in order to reach the group, she said, adding that it remained an "active scene".

"TAKE COVER NOW," the NWS warned residents of Portage, where the depot is located, earlier on Tuesday.

"Our thoughts are with those affected by the tornado in Portage, Michigan, and we are grateful there were no serious injuries resulting from the damage to our facility," FedEx said in a statement.

Severe weather across West Michigan has led to multiple tornado watches and warnings, as well as a severe thunderstorm warning.

A tornado emergency, the most severe type of tornado alert issued by the service, tells people that a tornado is imminent or has already been spotted in the area.

A lower tornado watch remains in effect for several counties in southeast Michigan, as well as parts of Indiana and Kentucky. — BBC