WASHINGTON - The number of patients harmed by contaminated medical scopes in recent years far exceeds previous estimates from federal regulators, according to a Senate health committee report issued Wednesday.

From 2012 to 2015, specialized devices known as duodenoscopes were linked to more than two dozen outbreaks of antibiotic-resistant infections that sickened at least 250 patients in the United States and Europe, the inquiry found.

It also details a woefully inadequate warning system, in which manufacturers failed to inform health officials to potential problems linked to their devices, hospitals failed to alert federal regulators promptly about outbreaks, and the Food and Drug Administration was slow to identify the problem and alert the public.

Among the hospitals listed as outbreak sites are two from Philadelphia: Fox Chase Cancer Center, with three patients infected, and Thomas Jefferson University Hospital, with eight. But Jefferson has said it found no proof that its "superbug" infections, in 2013 and 2014, were actually caused by the scopes. Fox Chase officials said Wednesday afternoon that they had not had time to review the 301-page report.

A committee member, Sen. Patty Murray (D., Wash.), whose staff began investigating the issue a year ago, said the 250-plus infections were preventable.

"Patients should be able to trust that the devices they need for treatment are safe and effective," Murray said in a statement.

"Unfortunately, this investigation makes clear that current policies for monitoring medical device safety put patients at risk, and in this case, allowed tragedies to occur that could have, and should have, been prevented."

Duodenoscopes are used in hundreds of thousands of procedures each year in the United States to drain fluids from pancreatic and bile ducts blocked by cancerous tumors, gallstones, and other conditions. The scopes, which are threaded down the throat, have an intricate design that can make them hard to disinfect between uses.

An outbreak involving contaminated scopes last year at Ronald Reagan UCLA Medical Center in Los Angeles left at least two people dead, and officials said scores of other patients potentially were exposed to dangerous bacteria.

In February, the FDA alerted doctors and hospitals that duodenoscopes can be difficult to disinfect between uses. The agency also sent warning letters to the manufacturers Olympus, Pentax, and Fujifilm, saying the companies failed to adequately report problems with the devices and, in some instances, failed to ensure that the scopes could be cleaned properly between uses.

The committee report spreads blame among manufacturers, hospitals, and the FDA, as well as what investigators say is an insufficient, outdated system of oversight that prevents health officials from spotting potential problems with medical devices in general.

Device makers failed to adequately test whether their scopes could be properly cleaned in a real-world setting, and didn't report problems quickly to regulators. Many hospitals also were slow to report infections to manufacturers and federal agencies.

And the FDA, in part hamstrung by an ineffective surveillance system, failed to spot the infections linked to contaminated scopes quickly or to alert the public. The report calls for legislative and regulatory changes to help officials identify and combat problems with medical devices.

The FDA said that it would "carefully consider" the recommendation's from Wednesday's report and that reducing the risk of deadly infections associated with duodenoscopes was a "top priority" for the agency.

"We agree with the senator that a broader approach to understanding how well duodenoscope devices work in real-time use is critical to public health," the agency wrote.

Mark Miller, a spokesman for Olympus Corp. of the Americas, in Center Valley, Lehigh County, said the company had cooperated with Senate investigators, providing documents and answering questions. "Although we do not agree with all of the report's conclusions, we are closely reviewing the recommendations in the report as part of Olympus' ongoing efforts to increase patient safety associated with use of Olympus duodenoscopes."

Staff writer Tom Avril contributed to this article.