A chemical spill in the Science Center early yesterday afternoon led to an immediate and complete evacuation of the building as authorities responded to the incident.

The spill took place a little after 1 p.m. when Graeme E. Dennis, the head teaching fellow (TF) for Chemistry 27, “The Organic Chemistry of Life,” dropped a glass bottle of hydrochloric acid while setting up for lab on the second floor of the Science Center.

The building was evacuated and remained so for about an hour and a half. Classes and sections usually held in the Science Center were cancelled until about 3 p.m. yesterday.

“It was a pretty standard spill,” Harvard University Police Department (HUPD) spokesperson Steven G. Catalano said. “This thing is minor.”

HUPD officers helped evacuate the building, and they were followed by the Cambridge Fire Department officers who were called onto the scene to neutralize the spill. Harvard University Department of Environmental Health and Safety also responded to the spill.

After the acid was neutralized, University contractors came in to clean it up.

“Basically, it was a very strong acid so it was causing lots of fumes,” said Camille I. Johnson ’06, a student in the class. “It smelled pretty bad.”

No one sustained injuries, but students said that some of the acid splashed onto Dennis’ shoes.

“Our head TF was in shorts,” said Sarah E. Kleinschmidt ’05, another student in the class who arrived right when the accident took place. “And he got some on his shoes.”

Chemistry students were asked to leave the lab and once in the hallway, Science Center alarms were sounded to evacuate the building. But students had a chance to “sneak back into the classroom,” and retrieve their possessions, said Kleinschmidt, who actually opted to leave some of her belongings in the lab.

The building remained closed for over an hour. And confused students mobbed the entrance to the Science Center, waiting anxiously in the rain to find out what prevented them from entering. Classes and sections that were supposed to take place during that time were cancelled. “I walked in five minutes before the section was about to begin and they told me that the building was closed,” said Julie B. Nantais, a TF for Science A-35, “Matter in the Universe.” She also said she waited after the evacuation to notify her students of the cancelled section.

Nantais said she was supposed to be taped for evaluation during yesterday’s section. But she said the evacuation did not inconvenience her. “It’s probably not going to be a problem unless there are no times when I can reschedule the taping,” she said.

Many students said they were not disappointed by class cancellations. Taking advantage of the free time, Kleinschmidt returned to her room to relax.

“I watched TV for the rest of the afternoon,” she said. “My notebook with my notes for all my classes was still in the [lab].

Students in the lab were not concerned by their exposure to the spill.

“None of us were really worried,” said Johnson. “We were all really excited that chemistry lab was cancelled.”

—Staff writer Claire G. Friedman can be reached at cfriedm@fas.harvard.edu.