WASHINGTON (AP) — Federal health officials are stepping up their oversight of medical scopes linked to potentially fatal superbug outbreaks.

The Food and Drug Administration released stricter guidelines for manufacturers of reusable medical instruments, including specialized endoscopes used in about a half-million U.S. medical procedures each year.

For the first time the FDA is asking manufacturers to submit scientific data showing that their devices can be safely disinfected. FDA officials acknowledged that previous agency guidelines from 1996 made no such request from companies.

The FDA had been working on the new device guidelines for years and previously issued a draft version of them in 2011. But the agency’s chief scientist, Dr. Stephen Ostroff, told reporters that the FDA “accelerated that pace because of the recent episodes.”

The government announcements come amid escalating criticism of the FDA’s oversight of the hard-to-clean devices, which have been linked to sometimes fatal outbreaks of antibiotic-resistant bacteria at several hospitals.

Additionally, the agency announced a two-day meeting for mid-May to gather expert opinion on improving the design and regulation of the so-called duodenoscopes. The specialized scopes consist of a flexible fiber-optic tube that is inserted down the throat, through the stomach and small intestine to diagnose and treat conditions in the pancreas and bile ducts.

Contamination problems have been reported with devices made by all three U.S. manufacturers of the devices: Olympus, Pentax Medical and Fujifilm.

Last week 10 members of Congress asked the FDA to answer questions about the devices, including how the agency reviews their cleaning instructions.

Rep. Ted Lieu, D-Calif., who has called for hearings on the issue, said Thursday that the FDA action was “an important first step.”

“However, further steps are needed and I will continue to push for mandatory reporting requirements, better resources for hospitals, and a new medical device which lessens the risk of infection,” said Lieu, whose district includes western Los Angeles.

In the last month, two Los Angeles hospitals have reported superbug infections in patients despite following manufacturer’s cleaning guidelines. The duodenoscopes’ complex design — intended to help physicians drain fluids in the body — also makes the instruments extremely difficult to clean. Bodily fluids and other particles can stay in the device’s crevices even after cleaning and disinfection.

In the first case, seven patients at Ronald Reagan UCLA Medical Center contracted an antibiotic-resistant strain of bacteria after undergoing endoscopic procedures with a device made by Olympus Corp. Two patients died from the infection. Last week another Los Angeles Hospital, Cedars-Sinai Medical Center, reported that four patients were infected with the same superbug after being treated with the same Olympus scope.

Previously the FDA recommended hospitals follow manufacturers’ instructions for disinfecting devices. But after the first of the two recent outbreaks, the FDA acknowledged that those instructions may not fully disinfect the devices.

Regulators stressed that using the devices is essential for treating tumors, gallstones and other blockages around the pancreas and bile ducts. FDA officials said Thursday they are working to see how the devices could be improved, but stressed that the FDA cannot force manufacturers to redesign products.

Additionally, outside experts said it could take years before any updated devices actually reach the market.

“Unfortunately, it’s going to take manufacturers some time to design a different way to do this,” said Chris Lavanchy, engineering director at the ECRI Institute, which studies medical product issues. “And then it’s going to take the FDA time to confirm that it’s a safer approach.”

Some hospitals have already adopted extra cleaning procedures, including sterilizing scopes with toxic ethylene oxide gas. Other steps include quarantining the scopes after use and performing laboratory testing to identify any dangerous bacteria.

The FDA and the Centers for Disease Control and Prevention issued interim guidelines on laboratory culturing for hospitals on Thursday.

The technique has become more common in Europe and Australia, but it is more expensive than standard U.S. practice. Experts say regular culturing of equipment would require U.S. hospitals to purchase larger inventories of scopes that can be cycled in and out of use. One duodenoscope can cost about $40,000.