Federal authorities on Friday opened seven new inspection booths for commercial traffic heading north to the U.S. from Mexico, nearly doubling capacity at the bridge that's the busiest commercial port on America's southwestern border — and a prime smuggling corridor for drug gangs.

U.S. Customs and Border Protection says the new posts will ease wait times on Laredo's World Trade International Bridge, where more than 4,800 18-wheelers rumble into American territory daily, or one about every 18 seconds.

The $5.4 million project also bolsters inspection of big-rigs that smugglers can cram with loads of cocaine, marijuana or amphetamines hidden among regular cargo. It includes two additional new lanes for "secondary inspection," an area with sniffer dogs where customs agents can provide extra screening.

"Laredo is about tractor-trailers, it's about commercial vehicles, so that's the environment the smuggler's going to try to work within," said Jerry Robinette, special agent in charge of U.S. Customs and Immigration Enforcement's San Antonio office, which oversee all of South Texas.

Laredo Mayor Raul Salinas joined his cross-border counterpart from Nuevo Laredo, Benjamin Galvan Gomez, and a gaggle of federal, state and local officials, who stood in front of the new blue-and-white inspection booths and cut a dark ribbon stretched symbolically across lanes marked "Fast 2" and "Fast 3." All around, thunderous and pungent lines of trucks waited to pass through the border.

Less than a minute later, a truck hauling water heaters rolled forward, the first to go through one of the new booths. Its driver, wearing a cap with a script "NY" on it, held out his passport in one hand and a copy of his cargo manifest in the other. He was taken aback when a half dozen of the grinning dignitaries reached up to shake his hand.

The bridge links top Mexican cities, including the northern industrial hub of Monterrey, with U.S. Interstate 35, a key artery for a highway system stretching across America. The expansion that broke ground in November 2009 is the bridge's first major upgrade since it opened in 2000 and increases its commercial inspection stations from eight to 15.

Laredo handles more commercial traffic than any other crossing point along the roughly 2,000-mile Mexico-U.S. border. The U.S. Department of Transportation says 60 percent of all truck traffic between Texas and Mexico passes through this city alone.

Exclusively for commercial vehicles, the World Trade bridge is Laredo's top commercial gateway, although two other local bridges handle some commercial traffic. Most of the 18-wheelers using it travel short distances between warehouses in Laredo and those across the Rio Grande in Nuevo Laredo. Long-haul trucks in Mexico and the U.S. head to the holding areas and drop off their cargo for the short hop across the border.

The bridge is so congested that customs can fully screen only a fraction of the trucks rolling through. That makes it a coveted drug-smuggling route, one so valuable that Laredo is at the center of a years-long turf war between the Gulf Cartel, which has traditionally controlled the area, and the Zetas, founded by Mexican military deserters who once served as Gulf Cartel enforcers but now run their own syndicate.

David Aguilar, deputy commissioner of Customs and Border Protection, traveled from Washington for Friday's ceremony. He said processing trucks faster won't make it easier for drugs to slip over the border but instead will streamline the process to better spot illegal loads.

"What we're looking for is that less than 1 percent that will take advantage of this type of flow for illicit activities," he said.

A brutal drug war has killed more than 34,600 people in Mexico since President Felipe Calderon announced a major offensive against traffickers when he took office in December 2006.

Monica Weisberg Stewart, chairwoman of immigration and land ports of entry for the Texas Border Coalition, said violence in Mexico has reduced traffic to and from that country in some border areas, but that wait times remain high because U.S. agents have responded to less-crowded crossings by reducing staffing. Her group represents border city mayors, county judges and economic development commissions.

"Congestion is huge," said Weisberg Stewart, who owns a business in McAllen, in the Rio Grande Valley southeast of Laredo. "It doesn't make any sense. If you have less people coming over, you should have less congestion."

Customs has not announced immediate staffing increases to ensure the new Laredo booths are fully occupied — but plans to add agents over time.

"It's similar to a Wal-Mart," Weisberg Stewart said. "You can have all these lanes. But the most frustrating part is you only have one or two open and there's all these lines backing up."