A Texas environmental group on Wednesday expressed public health concerns over reports of a "river of blood" flowing from behind a well-known meat-packing plant in Dallas.

Fox affiliate KDFW-TV reported last week that a criminal investigation is under way at Columbia Packing Co., Inc., after photographs surfaced showing what appeared to be pig blood flowing in nearby Cedar Creek, which feeds directly into the Trinity River.

Investigators from state and federal agencies determined that an unauthorized, underground pipe was draining pig blood into the creek from the back of the slaughterhouse, according to a search warrant obtained by the station. 

"It goes to show the length some companies will go to violate environmental laws," Zach Trahan, program director for the non-profit Texas Campaign for the Environment, told FoxNews.com.

"Building an underground pipe to take their industrial waste into a creek behind the plant is clearly against our clean water laws in this state and in this country," said Trahan, who blasted what he called an old "go-dump-it-out-back" attitude "still going on in this day and age in the heart of Dallas." 

Trahan described the 710-mile Trinity River, which flows entirely within Texas, as having a storied history of pollution.

"This isn't a good sign of our efforts to change that," he said.  

A member of the public taking pictures of the creek two months ago noticed a blood-like substance flowing in the water near the plant, according to KDFW-TV. The individual then reportedly notified the Dallas County Health Department, which took its own pictures revealing a dark red color in the water just downstream from the plant.

"When you look at these pictures, there's definitely something wrong with the discoloration," Zachary Thompson, with the Dallas County Health and Human Services, said of the aerial images in an interview with the station. 

Thompson said he alerted state and federal agencies who then executed a search warrant on the plant last week. The warrant reportedly confirmed the existence of an underground pipe and pig blood in the creek. 

"Why is that pipe there? Did it bypass the system?" asked Thompson.

He added that the city is looking to develop Trinity River for recreational purposes, like fishing and canoeing. 

On its website, the 90-year-old Columbia Packing company boasts about its "top quality pork" and "tender fully-cooked smoked Beef Brisket."

"We believe that business goes where it is invited and stays where it is well treated," reads a statement at the top of the company's site.

A representative from the company was not immediately available for comment when contacted Wednesday by FoxNews.com. The plant is reportedly still open while an investigation by the Environmental Protection Agency, U.S. Department of Agriculture and Texas Parks and Wildlife Department continues.

FoxNews.com's Cristina Corbin contributed to this report. 

Investigation: Pig’s Blood Flowing into Trinity River: MyFoxDFW.com