Amundson Hall re-opened Wednesday, a day after a chemical explosion triggered a fire sprinkler, flooding the third floor with more than 7,000 gallons of water.

Two University graduate students were injured when a small beaker full of tetrahydrofuran caused a minor flash explosion.

Graduate student Eric Cochran remained in the Hennepin County Medical Center’s burn unit Wednesday with a second-degree burn on his hand, said professor Frank Bates, head of the department of chemical engineering and materials science.

The heat from the flash explosion melted the student’s synthetic gloves onto his hands, Bates said.

Graduate student Thomas Epps suffered minor injuries and returned to work in Amundson Hall on Wednesday.

The students were distilling the flammable solvent when some of the vapors escaped the beaker and accumulated in the fume hood above the students’ workspace, Bates said. He believed an electrical switch inside the hood caused an ignition and a “flash fire” ensued, burning the students and activating a fire sprinkler located above the hood.

University officials evacuated the building and rescheduled classes for more than 400 students Tuesday.