Approximately 30,000 high school seniors received an e-mail congratulating them on their acceptance to the University of California, San Diego on Monday, only to find out hours later the university had made a mistake and that they had, in fact, been rejected.

The e-mail – which was meant to be sent to the 18,000 undergraduate applicants that had been accepted for UCSD’s 2009 Fall Quarter – was instead sent at 5 p.m. Monday to all 47,000 prospective students who had applied. The Office of Admissions soon realized their mistake and sent out a second e-mail explaining the situation, to the chagrin of thousands.

The letter began with a congratulatory opening that said, “We’re thrilled that you’ve been admitted to UC San Diego…,” and invited recipients to visit the campus for an orientation event. Admissions staff noticed the error approximately two hours after it was initially sent, at which time they sent out a second blanket e-mail informing recipients of the error.

For many of the nearly 30,000 students who had been rejected by the university but received the e-mail of congratulations, the announcement of the mistake was a disturbing and perplexing turn of events. Admissions staff members have been overwhelmed in recent days with e-mails from confused and outraged applicants.

Director of Admissions Mae Brown has issued a statement of apology to all those affected.

“We sincerely regret the confusion and distress our non-admitted applicants and their families may have experienced as a result of this error,” Brown wrote. “It was never our intent to cause further disappointment during an already stressful admissions process for high school seniors.”

In recent years, similar gaffes with admissions letters have occurred at Cornell University, the University of North Carolina at Chapel Hill and Northwestern University.