LAS VEGAS » A new report shows 200 people who dined at one of Las Vegas’ most popular restaurants about a block off the Strip have reported food poisoning symptoms, making it the largest outbreak southern Nevada health officials have seen in at least a decade.

Sick patrons who dined at Firefly, a tapas restaurant on Paradise Road in late April hailed from 20 different states and two foreign countries, according to a report released Friday by the Southern Nevada Health District. There are likely many more cases that have gone unreported.

"Usually we think of people who are identified as just the tip of the iceberg," said Linh Nguyen, an epidemiologist with the health district and lead investigator on the case.

Firefly is one of Las Vegas’ highest-rated restaurants on the review site Yelp.com, garnering a 4 ½ star rating on a five-star scale out of more than 1,300 reviews. Patrons rave about bacon-wrapped dates and signature sangria.

The restaurant has been closed since April 26, when health district officials received reports of gastrointestinal illness from eight separate groups of people who had dined at Firefly between April 21 and 24. Inspectors hit the restaurant with 44 demerits, including food stored at improper temperatures and employees handling food without gloves.

Firefly owner John Simmons said in a statement that he hopes to reopen by the end of the month at a different site near the old restaurant. He added that he’s hired a food safety consultant and is working to implement the district’s recommendations to regain the community’s confidence.

Already, a Las Vegas couple has filed a lawsuit against Firefly. Representatives of Seattle law firm Marler Clark, which specializes in foodborne illness cases, said today that a total of 76 people have contacted them hoping to be included in the suit.

In salmonella cases where a person has a few days of severe illness but fully recovers, a jury might award $5,000 or $10,000, lawyer Bill Marler said. That number can go up if the person spent time in the hospital, missed work, or had lasting complications linked to the illness.

A key element of the case will be determining whether the restaurant’s actions caused the outbreak, Marler said.

But two weeks after shutting down the restaurant and collecting food samples that ranged from macaroni and cheese to mussel sauce, investigators say they haven’t pinpointed a menu item or ingredient that’s the likely culprit.

Investigators initially zeroed in on an egg-based aioli sauce, but have since ruled that out. Some grated hard cheeses also appeared to be associated with the illness, although many of the menu items consumed by the patrons didn’t contain the cheese.

Inspectors are considering employee hygiene practices, and tracing back the sources of some foods served raw. If the salmonella originated further back in the supply chain, sickness may be showing up elsewhere in the country.

Nguyen said the restaurant’s popularity and vast menu may have contributed to the spread of salmonella.

"Sometimes when they’re very busy … employees might take shortcuts," she said.

Two other Firefly locations in the Las Vegas area remain open.