University officials expect to announce today the preliminary findings on the cause of the epidemic which caused more than 225 students to become violently ill last week, Harvard health officials said yesterday.

Thus far, health officials have found no common origin of the mysterious illness. However, incoming tests from patient cultures have now ruled out salmonella, shigella, campylobacter and yersinia strains of bacteria as a potential cause of the illness.

The possibility of botulism, food poisoning manifest in some canned goods, has also been ruled out due to the absence of neurological symptoms among the patients.

Today's preliminary results will reflect a compilation of all available data from a variety of sources. This includes information obtained from 340 questionnaires given to both affected and non-affected students as well as test results from the Centers for Disease Control and Prevention (CDC) in Atlanta and the Food and Drug Administration in Washington, D.C.

Officials cautioned that today's report may still not give a conclusive explanation. In fact, in 30 to 40 percent of the cases nation-wide dealing with food-borne epidemics, a traceable cause is never discovered, according to a statement released by the Harvard News Office.

And the epidemic may not be related to food at all. Incoming results point to a viral agent as the more likely cause, said Michael P. Berry, director of Harvard Dining Services.

"The recent outbreak may not have been a purely Harvard phenomenon, but an incident which had outside causes," Berry said.

Only two students showing symptoms typical of the gastrointestinal illness checked into the Stillman Infirmary yesterday, according to University Health Services reports. Officials did not know if these students were sick due to the epidemic.

Between six and 12 students per day had entered Stillman since last Wednesday. On average, four students check into Stillman daily because of gastrointestinal illness.

With meals now being prepared again at the Union, several precautions have been taken to enhance safety.

Most notable is the fact that the pasta and the eggs at the salad bar have been temporarily removed because tests showed that those two items did in fact contain abnormal amounts of bacteria, although not enough to have caused the epidemic.

Additionally, sanitation practices have been reemphasized to Union employees and a greater number of management have been staffed to answer any students concerns.

Investigations of the possible link of the Harvard epidemic with a similar epidemic experienced at Dartmouth College just 11 days ago are continuing but have been recently slowed down.

When Harvard requested that Dartmouth send a list of its food vendors so that a comparison might be made, Dartmouth refused to honor Harvard's request, Berry said. Harvard has subsequently contacted CDC in an attempt to force Dartmouth to release this information, Berry added