About 100 employees of the University of Maryland and the nearby American Center for Physics were struck by a violent gastrointestinal illness this week, officials said.

The outbreak infected nearly all of the faculty at the university's school of architecture and forced the closure of the physics center yesterday afternoon.

The victims' symptoms appeared similar to those of the norovirus that this month infected about 100 teenagers staying at the university's College Park campus for a youth leadership program.

University officials said the outbreak would not interfere with the beginning of school. Students began moving in Thursday and classes are scheduled to begin Monday.

Prince George's County health officials are investigating the illness but have not yet determined the cause. Frederick J. Corder, the county health officer, said he hopes to receive lab results tomorrow that will identify the source of the outbreak.

On Tuesday, about 50 faculty and staff members from the University of Maryland's School of Architecture, Planning and Preservation attended a retreat at the American Center for Physics in College Park. At noon, they ate a buffet-style lunch of assorted sandwiches, garden salad, potato salad and cookies, staff said.

The first victims felt ill the following evening. Angel D. Nieves, an assistant professor of historic preservation, said he woke up Thursday morning with nausea, diarrhea and an aching feeling.

He has been home sick for the past two days. "It pretty much knocked me out," he said.

Most of the teaching staff at the school of architecture were absent Thursday. The main orientation for architecture students took place, Nieves said, but several smaller group meetings were canceled because professors were home sick.

"It seems about 98 percent of the faculty have been hit," Nieves said.

About 40 employees from the American Center for Physics did not report to work on Thursday after suffering from similar symptoms, according to Bernard Khoury, the group's president. The center, made up of four nonprofit scientific societies, has about 200 employees at its College Park facility.

The building closed at 3 p.m. yesterday after an additional 10 employees fell ill, Khoury said. The entire facility will be disinfected over the weekend and could reopen as soon as Monday. But Khoury said employees should stay home if they feel ill.

"We have now urged people not to come to work after they feel stomach distress," he said. "We have told them not to come to work until you feel well for three consecutive days."

The norovirus, which has sickened hundreds of passengers on cruise ships in recent years, is extremely contagious.

It causes acute vomiting, diarrhea, cramps, nausea and a slight fever for 24 to 48 hours, though victims can sometimes remain contagious for up to two weeks.

The virus is contracted through surface contact and cannot be treated by antibiotics.

Corder said infection can be prevented by thoroughly washing hands after using the toilet or having diarrhea or vomiting and before handling food and drink.

Despite their norovirus-like symptoms, some architecture professors said they would not let the illness interfere with the start of school.

Alexander Chen, director of the urban studies and planning program, said he felt violently ill at 1 a.m. on Thursday. But he still decided to attend a student orientation later in the day after he started feeling better. "I did my vomiting in the morning," he said.

Other faculty members said yesterday that they would remain at home to make sure the illness would not spread.