A Dallas meat-packing plant cited for allegedly draining pig blood and other contaminants into a nearby creek called the situation "an accident" caused by a "clog in the sewer line."

Company officials also accused the city of failing to notify them about the so-called "backup" for 41 days, but a letter penned by an attorney for the city of Dallas reveals a slew of alleged health violations at the 90-year-old Columbia Packing Co., including industrial waste such as "hair and fleshings," blood and plastic gloves being discharged into the wastewater system.

Fox affiliate KDFW-TV reported last week that a criminal investigation is under way at the company 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. 

In a statement released to FoxNews.com on Thursday, the plant acknowledged a complaint about a "discharge of our industrial waste process flow." The company claims it was notified about the problem on Jan. 19 and "immediately cooperated with officials."

"We discovered that a clog in the sewer line had caused the flow to backup into an overflow vent pipe in the creek drainage area," the company said. "We were extremely disappointed that city was aware of the backup for 41 days before notifying us of  the problem." The plant went on to call the incident an "accident" that its owners and employees "deeply regret."

In response to inquiries on the matter, the city released a letter to FoxNews.com by city attorney Christopher D. Bowers to Amy L. Rickers, a lawyer for the company.

In the letter, dated Jan. 24, Bowers cites several alleged violations of city ordinances that he claims "may create health and safety problems for the employees, neighbors and the general public."

Bowers states that "runoff and/or washdown water from an animal pen and livestock containment area is being discharged into the stormwater drainage system." The letter also alleges that pollutants such as "hair and fleshings, whole blood, plastic gloves and other materials" are being released into the wastewater system. Bowers also cites "noxious odors or stenches" from the slaughterhouse as well "as holes, cracks and loose surface materials that are health or safety hazards in the floors, walls or ceilings." 

The letter demands that the company fix the violations before resuming operation. 

A member of the public taking pictures of nearby Cedar 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.

The creek feeds directly into the 710-mile Trinity River, which the city has been looking to develop for recreational purposes, like fishing and canoeing. 

"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. 

On its website, the 90-year-old Columbia Packing 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.

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