More than 100 people have been struck down by a gastro outbreak at the Sandown Park Greyhound Racing Club in Melbourne’s south-east.

Teachers and students were among the 100 people who fell ill following a valedictory function for Wantirna Secondary College at the club’s function centre last Wednesday.

Four people, including two teachers, needed hospital treatment for dehydration.

The club was closed for commercial cleaning the following day, but more people reported suffering vomiting and diarrhoea after attending the greyhound races on Friday night.

Marissa Notley, 50, said she felt ill just hours after attending a buffet dinner at the club for greyhound racing’s Melbourne Cup.

She said she ate lasagne, rice, chicken, potato, pumpkin, caesar salad and a small serving of tortellini.

“I felt unwell on that night … I went home and had cramps in my stomach and I didn’t have much of an appetite the next day,” Ms Notley said.

“By late Saturday night I was vomiting and had diarrhoea.”

Ms Notley said six other people who sat at her table had also fallen ill.

“That fact that people got sick the Wednesday night before has angered me a little a bit more,” she said.

Department of Human Services spokesman Bram Alexander said authorities were yet to identify the cause of the outbreak.

He said the department was testing samples to determine whether the outbreak was the result of a virus, or contaminated food.