More than 20 persons--four of whom were hospitalized--became ill yesterday, apparently as a result of food poisoning at South House Wednesday night.

Dr. Warren E. C. Wacker, director of University Health Services, said last night the victims all reported eating seafood newburg at Cabot and Whitman halls. The illnesses may have been caused by salmonella poisoning, which usually takes affect 10 to 12 hours after eating, he said.

A total of 11 persons went to UHS yesterday complaining of stomach cramps, nausea and other symptoms and four were admitted to Stillman infirmary last night, Wacker said.

Lynne Parshall '76, one of those hospitalized, said last night she had eaten just the scallops and the shrimp out of the newburg and that the scallops were "mushy and not well cooked." She said she ate around 6 p.m. Wednesday.

Patricia Wu '78, taken by the Harvard police to UHS on a stretcher yesterday morning and in Stillman last night, said last night she had eaten just one shrimp and one scallop and became "horribly sick" early yesterday morning. Wu also said she ate around 6 p.m.

George W. Westcott, production supervisor in the Radcliffe dining halls, said yesterday. "We're very careful about seafood. I was checking it myself at around six and I thought everything was fine."

The shrimp, whitefish, scallops, and sauce in the seafood dish were all cooked separately, he said, "so it could be any one of those."

Pam Smith, tutor in South House, said yesterday she became ill "with a vengeance" around 5 p.m. yesterday. Smith said she called UHS and was told that her illness was probably due to the seafood.

"The shrimp were okay," Smith said, "but the scallops were two or three minutes undercooked, and it only takes about two or three minutes to cook them."

Smith said her husband had eaten a half-hour earlier and did not become ill.

Wacker said if it is salmonella poisoning. "we will have to screen all the people serving food to see if there is a carrier."