Dallas ? Workers at Bradco Supply Corp. arrived one morning to find someone severed the heavy chain locks on the security fence at the Fort Worth shingle supply warehouse. Inside, empty wooden pallets were splintered and scattered across the floor.

They’d been robbed. Again.

Thieves have targeted Bradco Supply locations so much in recent months that company officials decided to add a unique splash of paint to the shingles’ packaging to help police track down the stolen roofing material.

Crooks nationwide have been stealing millions of dollars worth of shingles from companies this year, a sizable increase from years past. Previously, thieves would steal them from construction sites, but not on this level. They’re now getting ambitious, robbing warehouses — sometimes several semi-truckloads at a time — and hauling away hundreds of thousands of dollars in shingles. In Texas alone, at least $4 million worth have been stolen this year.

“It’s tremendously exasperating,” said Barbara Douglas of the Lumbermen’s Association of Texas and Louisiana. “Especially for the people that have been hit more than once. It’s like hitting them when they’re down because the building economy is so slow. Retailers really can’t take hits like this.”

Investigators believe some thieves are part of an organized operation, stockpiling the materials in anticipation of hurricanes, tornadoes and other roof-ripping storms that would heighten the demand for their stolen wares. Other thefts may be isolated incidents from people looking to sell the shingles to roofers for a quick buck. Also, the soaring price of shingles, which are petroleum-based products, has driven the demand for cheaper, black-market roofing material.

The thefts are forcing roofing companies to spend thousands of dollars on security cameras, lighting and closed-circuit television equipment.

“All it’s done is suck the energy out of us,” said David Larson, a vice president of DeSoto, Texas-based DW Distribution, a building materials supplier that has lost $60,000 worth of shingles this year to theft.

No law enforcement agencies track the number of shingle thefts nationwide. The Texas Department of Public Safety is working with police and sheriff’s departments to stem the heists, said spokeswoman Tela Mange. But every day, she said, the thefts — and losses — continue to mount.

In July, masked thieves were caught on tape in Atlanta sawing through ABC Supply Co.’s fenced-in warehouse and then using the yard’s forklift to load up a truck with shingles. Nearly $30,000 worth of materials were stolen and the thieves were never caught, said Bill Schuch, security chief for ABC Supply, one of the nation’s largest roofing supply distributors.

Since then, ABC Supply has installed more security cameras and fences and added GPS equipment to its vehicles.

Besides Atlanta, thieves have hit ABC Supply’s locations in Florida, North Carolina, South Carolina, California, Oklahoma, Louisiana, Connecticut, Maryland and Texas, Schuch said.