The Centers for Disease Control and Prevention (CDC) told Congress it left out 34 incident reports involving lab mistakes from information it provided to a congressional investigation in 2014, according to USA Today.

Steve Monroe, the CDC’s associate director for laboratory science and safety, said the failure to include the reports was “an inadvertent omission” caused by only including incident reports from its main Atlanta lab, where the agency is based, instead of all its facilities.

USA Today reported these omissions covered incidents from 2007 through 2011, mostly at the CDC Division of Vector-Borne Diseases facility in Fort Collins, Colo. The missing reports dealt with inventory issues, cases of potential exposure, and keeping specimens in unapproved areas when dealing with several agricultural viruses, like the Venezuelan equine encephalitis virus, a mosquito-borne pathogen.

The 2014 investigation into CDC labs had been launched due to mistakes which may have exposed dozens of people in its Atlanta facility to anthrax. With the new reports also dealing with pathogens which could be used as bioweapons, members of Congress are accusing the agency of “chronic negligence.”

“We're not talking one or two incidents, but 139 discoveries of select agents in unregistered locations,” said Rep. Fred Upton, R-Mich., chairman of the House Energy and Commerce Committee.

Monroe tried to ease congressional concerns by explaining the circumstances behind the 34 reports which hadn’t been disclosed. He said an intensive review of the Fort Collins lab found vials of specimens in unapproved, but still secure, locations.

On the incidents which potentially exposed workers to pathogens, Monroe said some involved workers finding a previously broken vial or breaking one while taking inventory. In all cases, he said the workers were wearing protective gear and no one was infected.