A University graduate student was severely burned after a minor chemical explosion Tuesday afternoon in Smith Hall, marking the second lab accident on campus in a month.

Approximately 100 students evacuated the building at 3 p.m. after a beaker full of ether exploded on the fourth floor and triggered the fire alarm.

The student, whose name was not released pending notification of his parents, was using the beaker in a research experiment, University officials said.

Minneapolis Fire Battalion Chief Jean Kidd said the victim was able to walk out of Smith Hall.

An ambulance then took him to Hennepin County Medical Center’s burn unit, where he remained in serious condition Tuesday night.

“His skin was burnt and peeling off a little bit,” said freshman Ade Solarin, who said he saw the victim walking down the stairwell of Smith Hall in his underwear after the explosion. “He was holding himself in pain.”

Witnesses said the student suffered “gruesome” burns from the waist down.

The victim is the third graduate student injured during a chemical accident this semester, which University officials said is uncommon.

Graduate student Eric Cochran suffered second-degree burns on his hand after a beaker full of tetrahydrofuran caused a minor flash explosion in Amundson Hall on Sept. 10. His colleague, Thomas Epps, also received minor injuries in the same incident.

“Accidents happen,” said Judson Freed, director of the University’s emergency management department. “If it was a freak accident, there is little we can change.”

After the first accident, a dysfunctional fire sprinkler poured more than 7,000 gallons of water inside Amundson, forcing University officials to close the building and reschedule classes. But the accident Tuesday did not damage Smith Hall.

University and fire officials did not know what caused the beaker of ether to combust Tuesday, but said the minor explosion occurred beneath a chemical fume hood.

Along with Minneapolis emergency medical technicians, a hazardous materials unit responded to the accident to check for toxic chemicals in the building.

After half an hour, students were allowed to return to their classes, some with their protective goggles still strapped to their foreheads.

The fourth floor remained closed Tuesday afternoon as University and fire officials continued their investigation.

University police blocked off a portion of Pleasant Street from Arlington Street to Washington Avenue because of the incident.