SLIPPERY ROCK — Students at Slippery Rock University who returned from Mexico Tuesday will not be allowed at the college's graduation ceremonies Saturday because of fears of the swine flu.

Instead, SRU is offering the 22 students an alternative small ceremony.

The students had spent about a month in Mexico City working as student teachers at a preparatory school for kindergarten to 12th grade. They returned to Slippery Rock two days early after schools there were closed because of the spreading flu.

"This was a very difficult decision since these students have done outstanding work and were looking forward to graduating with their classmates. However, given the unknowns, we have an obligation to protect others from what they believe is possible exposure to this virus," William Williams, provost and vice president for academic affairs, said in a news release announcing the change.

None of the students show signs of the flu. However, the college said graduation would fall in the middle of the flu's incubation period.

Slippery Rock has received hundreds of calls from students and parents who were worried about being exposed at the commencement ceremonies.

About 1,300 students are expected to be awarded diplomas in two ceremonies Saturday.