Federal authorities on Thursday slapped new financial reporting rules on 2,000 businesses in the Fashion District of Los Angeles in an effort to curtail suspected Mexican and Colombian drug money laundering after massive amounts of cash were seized in a raid.

The Treasury Department's Financial Crimes Enforcement Network issued an order requiring the businesses to report any transaction involving more than $3,000 in cash. The geographic targeting order — a tool used to track and deter money laundering — is one of the largest ever issued, said Jennifer Shasky Calvery, the network's director.

"We're hoping this is going to disrupt the ability of some of the most prominent drug trafficking organizations out there to launder and use their money to continue their illegal activities," she said. "Our goal here is to make it so they can't move their funds."

Authorities are serving 2,000 businesses with notice of the order, which will last six months, Shasky said.

The move comes after federal authorities raided dozens of businesses in the Los Angeles Fashion District last month and arrested nine people in cases involving accusations of money laundering through international trade.

During the raids, federal agents seized more than $90 million in cash and more than $30 million in bank accounts, in addition to real estate and extensive documentation, said Virginia Kice, a spokeswoman for Immigration and Customs Enforcement.

Federal authorities allege that businesses in the Fashion District received drug money in cash in exchange for clothing sold in Mexico, which enabled cartels to recoup their profits in pesos without any currency crossing the border or getting wired into a bank. Thom Mrozek, a spokesman for the U.S. attorney's office in Los Angeles, said investigators suspect Colombian drug traffickers are also laundering money in the district.

Companies are regularly required to report any cash transactions that exceed $10,000 to federal authorities, but tighter rules were sought for the Fashion District after the raid. The order takes effect Oct. 9.

Kent Smith, executive director of the LA Fashion District Business Improvement District, said the order covers about 75 percent of his district and affects a host of businesses selling goods ranging from apparel to flowers.

The district generates more than $10 billion in economic activity each year, Smith said. Many of the businesses don't export but are still affected by the rule, he noted.

"It is a very blunt instrument," Smith said, adding that many businesses are small family-owned entities that work largely in cash. "It sends out a message to the world that these businesses are somehow involved in illegal activity, which is just not the case."

He said he would be "shocked to see the people involved in money laundering ... filling out their U.S. Treasury form."

Jere Miles, deputy special agent in charge of ICE's homeland security investigations in Los Angeles, said reducing the amount of cash a business can receive without reporting the transaction to authorities will make it tougher to disguise suspicious transactions from banks and investigators.

"It is also helping us send a message to people and say, don't get involved in this. This is what happens," Miles said.

A geographic targeting order was issued earlier this year for cash couriers and armored cars at two Mexican border crossing points in California.

In some instances, orders are not made public to facilitate law enforcement investigations. Shasky said the order is a tool that has not been used often, but she expects that could change.

"It is one that we are interested in, and our law enforcement partners are interested in using more and more," she said.