 -- The Centers for Disease Control and Prevention is investigating whether limb weakness and paralysis in nine children could be connected to the far-reaching outbreak of the respiratory disease Enterovirus 68.

The CDC released a statement today saying nine children in Denver had reported a neurologic illness that led to some limb weakness or paralyzation. All of the children had reported having a kind of respiratory virus before showing symptoms of limb weakness.

Six of the eight children tested were found to be positive for a rhinovirus or enterovirus and four of those cases were found to be the Enterovirus 68. The other two cases were still pending.

Dr. Larry Wolk, the chief medical officer and executive director for Colorado Department of Public Health and Environment, said that the children affected range in age from 1 to 18, with an average age of 10.

"It is a spectrum of arm or leg weakness that can be as mild weakness or as severe as paralysis," Wolk said. "What ties them all together though are findings of spots or lesions in the grey matter of the spinal cord on MRI scans."

Medical officials have not determined whether the Enterovirus 68 virus caused the neurological symptoms, but the CDC is asking other medical workers to report any similar cases as the outbreak of the enterovirus 68 continues to spread throughout the U.S.

According to the report, there were signs of infection in the spinal fluid, but no evidence of a specific virus in the spinal fluid. Tests for viruses that could cause similar reactions including West Nile and Polio were negative.

Wolk cautioned that parents should be aware but not panicked by the findings.

"It's a pretty rare complication and not unexpected with this kind of viruses," Wolk said. "You hear about this nine with this complication, what you're not hearing about is that thousands or hundreds of thousands" just have a cold.

Dr. William Schaffner, an infectious disease expert at the Vanderbilt University School of Medicine, said he found the report "sobering" but that more research needs to be done to discover the cause.

"From time to time other Enteroviruses can behave very sporadically like the polio virus," Schaffner said. "The leading candidate is indeed this Enterovirus D-68. Having said that ... further investigations are going on with the children."

Schaffner explained the CDC alert will help officials figure out the scope of the problem and to see if it can be attributed to the enterovirus 68.

The enterovirus 68 has been reported in at least 40 states and confirmed in at least 277 people according to the CDC. However, since the symptoms of the virus, which can include coughing, fever and runny nose, can appear mild, the number of those infected could be exponentially larger than what has been reported.

The virus has appeared to have more of an effect on some children with asthma, leading a small number to need help breathing. No deaths have been attributed to the virus in this outbreak.