Investigators say the number of these corrupt businesses is small, but they play a significant role in helping illegal immigrants reach the country's interior.
The accomplices have included landlords and rental agents who provide homes for smugglers to hide immigrants; taxi drivers near the border who bring immigrants to the closest cities; used-car dealerships that let smugglers register vehicles under false names; and travel agencies that sell blocks of plane tickets for immigrants.
"At every stage along the way, a process has been taken over, corrupted, in order to facilitate the transportation" of illegal immigrants, said Arizona Attorney General Terry Goddard, whose office has prosecuted such cases.
Authorities are unable to estimate the number of businesses helping smugglers but say the biggest concentration is in Arizona, the busiest illegal gateway into the United States. Immigrant smuggling in Arizona is believed to be a $1.7 billion-a-year business.
Businesses also are cooperating with smugglers in San Diego, Los Angeles, Houston, San Antonio and El Paso, Texas.
Immigration agents said some of these accomplices are criminal operations through and through. But others are bona fide businesses willing to break the law now and then for the extra bucks.
Authorities have prosecuted only a modest number of businesses, saying smuggling operations are often family-run and difficult to infiltrate with informants or undercover officers. Also, recorded conversations are needed to prove that businesses knew they were breaking the law.
The businesses "are willfully blind to what on the face should be obvious," said Alonzo Pena, chief of investigations for U.S. Immigration and Customs Enforcement in Arizona. But "we can't convict someone for willful blindness. We have to show an actual element of knowledge or intent."
One success was a 2005 case in which undercover agents posing as smugglers were rented rooms at six motels in Mesa, Ariz. The motel operators were accused of coaching the agents on how to conceal their illegal activities.
In 2004 and 2005, 16 people associated with car lots in Arizona were convicted on various charges of helping smugglers.
No entire industries or national companies have been corrupted, and the complicit businesses represent a small piece of any given industry, investigators and prosecutors said.
Still, prosecutors said that smuggling assistance accounted for 85 percent of one Arizona travel agency's business and that some used-car lot operators convicted of working with smugglers had almost no legitimate sales.
In some cases, the managers of businesses are unaware their employees are helping smugglers.
For example, some car rental agents, acting without their bosses' knowledge, allow smugglers without credit cards to rent vehicles and require large deposits to cover towing fees if the vehicles are seized by police, authorities said.
A lot of the illicit assistance involves transportation.
In a 2004 case, smugglers went to low-end used-car lots in Phoenix to obtain vans and SUVS. For a fee, the car dealers masked the vehicles' true ownership, removed back seats to pack in more immigrants and installed shocks to handle heavier loads.
Dealers have also been known to put fake liens on vehicles so they would revert to the car lots if the immigrants got caught by police. That allowed the vehicles to be recycled back into the smuggling operations.
Another option for smugglers is to hire small van companies in Houston, San Antonio, Los Angeles and Phoenix to drive illegal immigrants to destinations throughout the country at exorbitant prices.
Some travel agencies in Phoenix, San Diego and Los Angeles are suspected of knowingly selling plane tickets to smugglers.
Last spring in Arizona, six travel agencies were accused of working with smugglers, and authorities estimated the businesses sold tickets for an estimated 6,800 illegal immigrants over nearly two years.
In stings at the agencies, undercover officers made it clear they were getting tickets for illegal immigrants and bought one-way tickets with cash. The travel agencies offered advice on being discreet at airports, authorities said.
Smugglers use two approaches to get businesses to help them: They infiltrate travel agencies and other businesses by getting relatives or fellow smugglers jobs there. Or they approach business owners or their employees in a friendly way, offer to buy lunch and see whether they can be corrupted.
Nevertheless, when an illegal scheme is busted by authorities, the smugglers always seem to find a creative new way to do business.
"There is no such thing as a checkmate," said Elise Green, a U.S. immigration agent, "because as soon as you take out one of the pawns, there's another pawn right behind it ready to take over."