A drone enthusiast testing out his airborne camera discovered a river of blood behind a Texas meatpacking plant, prompting outrage and investigations by local authorities.

"We were very concerned with the fact that this discharge was going into the creek which is going into one of our treasures -- the Trinity River," Zachary Thompson, director of Dallas County Health and Human Services, told AFP.

"People should be able to use it as a fun and recreational area. You don't want to see it impacted by any kind of discharge."

Especially not pig blood.

"I was looking at images after the flight that showed a blood red creek and was thinking, could this really be what I think it is? Can you really do that, surely not? " the drone operator told sUAS News -- an online magazine for small unmanned aerial system enthusiasts.

"Whatever it is, it was flat out gross."

The plant operator said the spill was caused by a clogged sewer pipe and lashed out at the city for waiting 41 days after the drone operator called in his report to do anything about it.

"If the city had contacted us on December 9, the problem would have been fixed on December 10," Joe Ondrusek, whose family has run Columbia Packing for 99 years, said in a statement.

He insisted that the spill was unintentional and noted that the city installed a box on the plant's sewer line years ago that monitors the amount of waste water going through the line and the substances contained in it.

A spokesman for the city of Dallas's attorney -- who has reportedly filed charges in the case -- did not return a request for comment.