Zebra mussels have been found in the Lake Ray Roberts, north of Denton, Texas.

The tiny mussels have become an invasive species across several countries causing damage to boats, ships, harbors, power plants and waterways. This is the second time that mussels have been found three years after they were discovered in Lake Texoma in Texas.

"Unfortunately, from an environmental and economic standpoint, this is very bad news," said Texas Parks and Wildlife Department Executive Director Carter Smith in a news release.

"For a host of reasons the implications of this discovery are substantial to Texas waters and their future use and management. We intend to continue working with our partners to do everything reasonably possible to try and prevent the further spread of this harmful invasive species."

Experts took DNA analysis of the samples taken from 14 of the Texas reservoirs and found that the zebra mussels were present in two lakes - Lake Ray Roberts and Lake Texoma. All the other 12 lakes tested negative in the analysis.

The mussels are said to be as small as 1/8 to ¼ of an inch in size. The experts have been baffled as to how the mussels reached the lake. Some believe that the boats that traveled to Texoma may have carried the mussels to lake Ray Roberts.

"More than likely, it was a boat that operated in Lake Texoma or some other lake infested with zebra mussels and then was used in Lake Ray Robertswithout first being cleaned, drained and dried," said Gary Saul, TPWD Inland Fisheries Division Director, in the press release. "In reality, we'll probably never know."

While the experts have not been able to stop the spread of these mussels, they have been able to slow down the spread using ways such as preventing the boats that have been used in lakes infested with mussels to be used in other lakes.

The boaters have been asked to clean and drain the water from their boats before moving to another lake.