) -- Insider trading may be a new risk to international dealmakers seeking to buy U.S. companies, as regulators begin a review of what could be the largest-ever acquisition by a Chinese buyer of a U.S. firm.

In a Thursday complaint, the

Securities and Exchange Commission

brought forward allegations a Thai trader may have illegally profited from inside information about the recently announced

proposed purchase


Smithfield Foods



Shuanghui International Holdings


The allegations come after a string of similar complaints involving acquisition efforts by emerging market firms for North America companies, and raise the prospect that insider trading concerns could put a damper on international mergers.

In the wake of Smithfield's announced acquisition by Shuanghui for $4.7 billion, most media reports are focusing on how the deal among pork industry heavyweights will test regulators' resolve to allow Chinese firms to invest in the United States. Senators, regulators and the Committee on Foreign Investment in the United States (CFIUS) will take a close look at whether Smithfield's acquisition raises national security concerns.

A bigger issue, however, may be the rash of insider trading allegations after the SEC said Thursday it froze the assets of a Thai trader who the regulator


made an illicit profit of $3 million on a tip about Smithfield's sale to Shuanghui.

Other large cross-border deals, notably



pending acquisition by

Berkshire Hathaway

(BRK.A) - Get Report


3G Capital

of Brazil and


(CEO) - Get Report

acquisition of Canadian oil and gas driller



have also been bogged down by

insider trading inquires


Allegations of impropriety tied to such high profile deals could cool U.S. firms' interest in selling to foreign buyers, given less strict regulation in emerging markets such as China and Brazil.

The allegations may also give U.S. regulators new reasons to be skeptical of foreign acquisitions of U.S. firms, beyond traditional CFIUS reviews.

To be clear, none of the companies involved in large recent deals are accused of any wrongdoing.

Instead the SEC allegations or inquiries target brokers, bankers and traders who may have benefitted from non-public inside information in trades prior to the announcement of each deal.

In Thursday's allegations, the SEC claims Badin Rungruangnavarat of Thailand purchased thousands of out-of-the-money Smithfield Foods call options and single-stock futures contracts from May 21 to May 28 in an Interactive Brokers account after receiving material, nonpublic information about the firm's potential acquisition.

The SEC's complaint states that one of Rungruangnavarat's sources of non-public material information was a Facebook friend who is an associate director at an investment bank a company that was exploring an acquisition of Smithfield.

The insider trading allegation connected to the Smithfield is similar an investigation made by the SEC related to

Heinz's takeover


The SEC alleged in that merger a dormant trading account in Switzerland bought call options for Heinz just ahead of the ketchup maker's


by Berkshire and 3G Capital, in what the regulator said was a violation of securities laws.

The SEC alleges that on Feb. 13, a day prior to the announcement of Heinz's acquisition, the Swiss options account bought 2,533 out-of-the money June $65 calls for a total of nearly $90,000. "Between Sept. 1, 2012, and Feb. 13, 2013, the account through which the defendants traded had no prior history of trading in Heinz," the SEC states.

When Heinz's $72.50-a-share acquisition was announced, those trades stood to gain nearly $1.8 million, a 1,700% return from the prior day when the contracts were traded. The alleged insider trading traced back to an account at

Goldman Sachs

, however, it's owners didn't appear at a U.S. court hearing freezing the account's assets and a criminal inquiry is ongoing.

In November, Brazilian ex-banker Igor Cornelsen and his firm Bainbridge Group agreed to pay $5.1 million to settle SEC allegations that he made illegal trades ahead of 3G's 2010 acquisition of Burger King Holdings after receiving an insider tip from a Wells Fargo broker in Miami.

The SEC is also investigating Hong Kong billionaire Zhang Zhirong's millions in options trading profits on CNOOC's acquisition of Nexen for $15.1 billion, according to a July 2012


brought forward by the regulator. According to the complaint, the SEC's investigation continues, however it has frozen the account's assets.

The string of insider trading allegations and inquiries in some of the most notable recent cross-border merger efforts in North America indicate risks beyond simple national security issues.

While the Smithfield Foods acquisition may be a bit of a lightning rod for fears about foreign ownership of U.S. firms, the insider trading allegations that have come with the acquisition may raise new concerns for investors, regulators and C-Suites.

-- Written by Antoine Gara in New York

Follow @antoineGara