LAS VEGAS (KLAS) — Preliminary lab results suggest that norovirus was the cause of a reported mass illness at Tanaka Elementary School nearly two weeks ago, according to the Southern Nevada Health District.

A gastrointestinal illness outbreak infected an estimated 130 students at the school, sometime during the week of Jan. 23 to Jan. 27, according to a letter sent to parents and guardians from the Clark County School District. It remained unclear Monday which day the students became sick.

A source close to the school previously claimed the students were simultaneously vomiting.

“A teacher said it was like Armageddon. Our daughter said there were trash cans lined up and kids just throwing up everywhere,” a parent told 8 News Now.

Norovirus is very contagious and can spread through direct contact with an infected person, by consuming food or water that has been contaminated, or by people touching contaminated surfaces and then putting their unwashed hands in their mouths, SNHD said.

“During a foodborne illness outbreak, people are interviewed about what they ate before they got sick when possible food contamination is confirmed using epidemiological and laboratory information,” a spokesperson for SNHD previously said in a statement. “Gastrointestinal illnesses can have many causes.”

Common symptoms of norovirus are diarrhea, vomiting, nausea and stomach pain. Symptoms can also include fever, headache and body aches.

A final count of exactly how many people were sick due to the outbreak has not yet been confirmed, SNHD said Monday.