Real estate broker Cyle Young got a shock when he drove by a house he bought two days earlier.

The home had been stripped of aluminum siding from the ground to as high as a person could reach.

"A couple days later, they broke back in and stole all the copper in it," said Young, who has since renovated the house and has it up for sale. "I can't tell you how many houses we've bought with no downspouts — gutters gone."

High market prices for copper and aluminum are enticing thieves to steal metal to sell for scrap. Fueled in part by a building boom in China, demand for copper has pushed its price to historic highs, and aluminum prices are the highest they've been in 17 years.

Demand for copper has increased by 4 percent a year since 2002 and expected to continue at that rate for the next three or four years, according to Robin Adams, managing consultant for CRU Strategies in Seattle.

Demand for aluminum grew nearly 10 percent in 2004 and 4.6 percent in 2005 and is expected to increase 4.5 percent this year, he said.

The theft of metal pipes, radiators and wires out of vacant homes is nothing new. Authorities have long blamed it on drug addicts looking to pay for their next fix. Now police are being inundated with reports of metal thefts.

In Springfield in western Ohio, thieves hit about 70 homes and businesses in five months. In other parts of the country, they carted off air conditioners from an apartment complex, stole downspouts from a church and snipped down cables for a tourist trolley.

In some cases, thieves have masqueraded as construction workers.

"This is just crazy," said Springfield police Detective Geoff Ashworth, who is taking up to two metal theft reports a day. "And there's no one or two, there's no six people that are specifically responsible for this. Everybody's doing it. People know the prices are up."

On the market, pure copper is selling for about $2.10 a pound, and aluminum about $1.05. Scrap copper, such as pipe and wire, is fetching between $1.30 to $1.80 a pound, about double what it was a year ago. Medium-grade scrap aluminum, such as siding, sells for 45 to 65 cents a pound, up 10 to 12 cents.

Mary Poulton, head of the department of mining and geologic engineering at the University of Arizona, said the price of copper is likely to remain high for some time.

"Given how long it takes for new production to come on line, we're seeing forecasts that we are looking at a 20- to 30-year high-price cycle," Poulton said. "And some analysts say $3-a-pound copper is not out of the question."

The theft problem isn't confined to the United States.

Taiwan's state-run power firm says the theft of power lines for their copper wire increased so much in 2005 that the company has replaced the lines with less expensive aluminum.

Law enforcement officials believe the thefts have increased in part because people are going through tough economic times. And some targets are new since metal prices have climbed, including farm irrigation equipment in Minnesota and Nebraska.

"They're pretty innovative about what they can steal and sell," said Todd County (Minn.) Sheriff David Kircher.

A two-mile stretch of streetlights are dark in Tucson, Ariz., after thieves made off with 8 miles of copper power cable that will cost about $250,000 to replace.

"We have not seen anything like this," said Steve Pageau, deputy director of the Tucson transportation department.

About $35,000 worth of air conditioners was stolen from an apartment complex in Montgomery, Ala., for the copper coils inside.

"We arrested a guy who went out to a church and stole all the copper downspouts," Montgomery Police Lt. Huey Thornton said. "It's definitely something that has increased. It's turned out to be a thorn in our sides."

It can be tough to catch up with the culprits.

Disguised as construction workers, thieves often wear gloves, making it difficult to lift fingerprints.

Thieves with spiked boots climbed power poles just outside Yakima, Wash., to cut down 600 feet of copper cable for historic trolleys that carry tourists through a hillside gap, closing the ride for the season.

Some scrap dealers fear losing business if they grill customers about where they got the metal, said Ashworth, the detective in Springfield. He is trying to persuade them to install video cameras to help police identify customers who bring in metal that matches items reported stolen.

The theft problem has gotten so bad in Tucson, where a solar heating store has lost several thousand dollars in metal tubing and mounts for heating panels, that the City Council is backing an ordinance requiring junk dealers to give police the identities of people who sell scrap metal.

The council voted 7-0 in favor of the idea and will vote on a final proposal once the exact language is hammered out.

The Institute of Scrap Recycling Industries sends dealers alerts when large amounts of metal are stolen to help them avoid buying it, spokesman Bob Garino said.

"The last thing they want is to be hassled by local authorities for stolen material," Garino said. "These guys know their customers. If suspicious, they'll act accordingly."

Young estimates the thefts at his Springfield properties have cost him $5,000. His real estate company is now waiting to purchase homes until a remodeling crews are ready to occupy them, he said.

"You don't want vacant houses right now. It's a nightmare," he said.