A federal investigation has been opened into the source of the illegal downloads of Lionsgate action pic The Expendables 3, according to sources with knowledge of the matter. The U.S. Department of Homeland Security’s Immigration and Customs Enforcement, aka ICE, has picked up the case after Lionsgate made calls to several law-enforcement agencies to ask for help in locating the pirates, who are accused of leaking a full version of the pic on various file-sharing sites last week. U.S. Customs was merged into USDHS, and it investigates illegally distributed copyrighted materials, including media content. In the past it has actually seized domain names of websites used to illegally distribute media content and/or counterfeit goods. Said an ICE public affairs officer this afternoon, “It is our policy to neither confirm or deny that an investigation is underway, unless or until it results in some type of public enforcement action.”

It comes the same day Lionsgate filed suit against the sites hosting the pic and the same day it dropped the final trailer (see it below) that opens wide August 15.

Lionsgate found out about the theft of a single digital copy last Friday, according to the suit, with news of the download surfacing wide by the time Comic-Con was in full swing last weekend. We’re told there were 250,000 downloads on that first day, and Variety reports piracy-tracking firm Excipio says there have been 2 million downloads to date.

In the suit, the studio names file-sharing sites Limetorrents.com, Billionuploads.com, Hulkfile.eu, Played.to, Swantshare.com and Dotsemper.com and claims it sent several letters to each site demanding the movie be removed. It demands a temporary restraining order, a preliminary injunction and a permanent injunction as well as actual and statutory damages. The first two installments of the franchise have grossed $580M worldwide.

The latest pic returns many veterans of the series — Sylvester Stallone, Arnold Schwarzenegger, Jaosn Statham, et. al. But there also are several newcomers including Mel Gibson, Wesley Snipes, Antonio Banderas, Kelsey Grammer, Harrison Ford, Kellan Lutz and MMA star Ronda Rousey.