Authorities say more than 100 burglaries of Houston-area pharmacies have occurred since June, resulting in the losses of millions of dollars worth of prescription drugs.

Ten people have been charged in the burglaries and authorities say at least 20 others are believed to be involved.

Most of the burglaries are targeting “mom and pop” pharmacies where drugs such as Soma, Xanax, hydrocodone and codeine-based cough syrups have been stolen, said Lt. Rebecca Follis of the Houston Police Department’s burglary and theft division.

In Houston, the drugs have a street value of about $4.5 million, said Lt. Dan Webb with the Texas Department of Public Safety.

The drugs are being found by authorities in traffic stops around the state and the country.

“We want to stop it here,” Webb said. “Stop it from spreading and ensure it doesn’t affect the rest of the state.”

While the prescription pills sell on Houston streets for $1 to $1.50 per pill, Webb said in other cities where these drugs are more difficult to get, they can sell for $7 to $12 each.

Authorities believe the burglars work in groups of two to three. They wear baseball caps and scarves to hide their identities from surveillance equipment, Follis said.

“They usually occur after the store closes and they usually break in through an adjacent building or break down a door or window,” she said.

Police have declined to release the names of those already charged in connection with the burglaries, citing the ongoing investigation. The most recent burglary happened Oct. 8.

No one has been injured in any of the burglaries.

Crime Stoppers is offering up to a $5,000 reward for information leading to the identification, arrest and prosecution of people involved in the burglaries.