The FDA is warning that ERCP endoscopes may allow for the transmission of certain drug-resistant “superbugs,” even if the devices are properly cleaned.

The advisory was issued in the wake of news that contaminated endoscopes are suspected of causing a deadly outbreak of the superbug CRE, or carbapenem-resistant enterobacteriaceae (CRE), among patients at the UCLA Ronald Reagan Medical Center in Los Angeles.

According to the LA Times, UCLA has confirmed that seven patients who underwent procedures with the scopes were later found to have contracted CRE. Two of the patients died. The hospital revealed Wednesday it is offering screening tests to 179 other patients who have undergone similar procedures since October.

The devices, also known as a duodenoscopes, are long, illuminated tubes that are inserted into the mouth and maneuvered through the esophagus to the small intestines. The scopes, which often feature tiny cameras, are used for a variety of procedures involving the intestines, pancreas, gallbladder, liver and stomach.

According to the FDA, the devices feature crevices that can harbor pathogens, such as CRE and E. coli, even after rigorous cleaning and disinfection. The agency is advising healthcare professionals to alert patients to signs of possible infection and to consider taking the scopes out of service until they are confirmed to be pathogen-free.

The devices are marketed in the U.S. by Fujifilm, Olympus and Pentax, the agency said.

From January 2013 to December 2014, the FDA received reports that approximately 135 patients may have been exposed to dangerous pathogens through duodenoscope procedures. The agency added the actual number of patients at risk could be higher.

The FDA estimates that roughly 500,000 procedures are performed annually using ERCP endoscopes.