Raleigh, N.C. — A law to help fight methamphetamine labs has blocked more than 1,600 questionable medication sales in its first 11 days on the books, North Carolina Attorney General Roy Cooper said Thursday.

Under the law, pharmacies use an electronic tracking system, the National Precursor Log Exchange, or NPLEx, to log all purchases of products containing pseudoephedrine, which is found in common cold remedies and is the key ingredient needed to make meth.

State Bureau of Investigation agents and other law enforcement officers can analyze information from the tracking system to help identify possible meth labs based on repeated attempts to purchase the medications.

Previously, people involved with meth labs would shop at multiple stores and cross state lines to skirt state laws limiting pseudoephedrine purchases to two packages at one time and three within 30 days. The tracking system automatically lets retailers know if someone has reached the legal limit for pseudoephedrine purchases so the store can stop the sale.

The system links North Carolina with 18 states across the country, including South Carolina, Tennessee, Alabama, Florida, Kentucky and West Virginia. More than two-thirds of pharmacies in North Carolina are using the system, and more are in the process of joining.

So far, the system has blocked 1,669 questionable purchases of more than 2,000 boxes of pseudoephedrine in North Carolina, Cooper said. That’s enough pseudoephedrine to make approximately 3.8 kilograms of meth, he said.

“We’re making it more difficult for criminals to get the ingredients they need to make meth and easier for law enforcement to find them and shut down their dangerous labs,” Cooper said in a statement.

Last year, the SBI busted a record 344 meth labs statewide. That was up from 235 in 2010 and 206 in 2009.