PALM BEACH GARDENS, Fla. (AP) _ A tornado that surprised forecasters carved a 3-mile path of destruction, damaging or destroying 500 homes but causing only minor injuries. Gov. Jeb Bush declared an emergency Friday morning that sent state workers to help assess damage and render aid.

Most of the damage in Thursday afternoon's storm was in Riviera Beach and Palm Beach Gardens. The twister flipped over two tractor trailers, blew railroad boxcars off the tracks and tore the roof off a Pepsi plant. Some 400 homes remained without power Friday, officials said, down from 30,000 originally.

``I'll tell you truly, I was scared,'' said Riviera Beach resident J.R. Brown, surveying the damage as police cars roamed the streets. ``There was so much thunder and the wind was blowing, the trees were bending and all this debris was blowing around. I was trying not to look outside.''

The heaviest damage appeared to be at the A Garden Walk mobile home park, where several of the 420 units were destroyed. Others lost their roofs or sustained damage when old oak trees crashed onto them, trapping some residents until they were rescued. A gas leak temporarily forced out 200 residents.

``The streets look normal to the left, and you look right and it looks like Hiroshima,'' Donald Garcia said Friday. His home was spared.

``It's going to be more than a cleanup _ people's whole lives are gone,'' he said. ``It's lucky that everyone got out alive. That's the miracle of this.''

The tornado had winds of 73 to 112 mph, or an F1 on the Fujita scale, which ranks the strength of tornadoes on a scale ranging from F0 as the weakest to F5 as the strongest, said Rusty Pfost, meteorologist in charge at the National Weather Service in Miami.

Forecasters were surprised at the rapid development of the system and because tornadoes normally do not form in South Florida in August, Pfost said.

``Everyone is very lucky that nobody was killed,'' Palm Beach County sheriff's spokeswoman Diane Carhart said.

Looting was reported in Riviera Beach, and Palm Beach County Sheriff Ed Bieluch sent out extra deputies to guard against looting and other crimes. Two suspected looters were arrested late Thursday in an industrial park near the mobile home park, officials said.

At Driftwood Plaza in nearby Jupiter, the thin metal roof covering 32 stores was damaged, said Tammy Goodwin, who owns the Coastal Massage Day Spa. Signs were toppled in the high winds and some cars were covered in debris, she said.

``We were right in it,'' Goodwin said. ``Pieces of the roof were flying off.''

The National Weather Service said the tornado was spotted at 5:13 p.m. and cleared out by 5:40 p.m.