A structural engineer deemed the 20-year-old ocean sciences building at the University of Hawaii at Manoa safe Thursday, a day after an explosion rocked the basement laboratory, badly injuring a researcher, according to a UH official.

University officials announced that the Pacific Ocean and Science Technology building was to reopen today.

Officials had shut down the structure following Wednesday’s blast in the laboratory where a 29-year-old visiting researcher sustained arm injuries and possible facial burns. She was taken to the Queen’s Medical Center in serious condition.

Hawaii News Now identified her as Thea Ekins- Coward, reporting that she had lost an arm.

Honolulu Fire Department Capt. David Jenkins said the preliminary estimate of damage to the building is $1 million. The Fire Department has since handed over the investigation to UH.

Jenkins said he expects the damage estimate to increase after the university conducts a full assessment of the building’s contents.

At a news conference Thursday, Manoa Chancellor Robert Bley-Vroman said, “Our thoughts and prayers are with the individual who was injured.”

The injured women is a visiting researcher at the Hawaii Natural Energy Institute, a research unit of the School of Ocean and Earth Science and Technology. The laboratory is operated by the institute and focuses on renewable energy and biodegradable bioplastics.

“An experiment was in progress to grow cells by feeding them a mixture of low-pressure hydrogen, carbon dioxide and oxygen,” said Brian Taylor, dean of the school. “Since 2008, when the project began, the process has been used almost daily and without incident. Clearly, something unexplained happened last night.”

The visiting researcher, who has been working on the project for at least six months, was alone in the laboratory when the blast happened.

University officials said she is familiar enough with lab procedures to work efficiently on her own. Roy Takekawa, director of the university’s Environmental Health and Safety Office, said the researcher took the office’s general laboratory safety course on how to properly handle and store gases. She also underwent specific training in the procedures of the laboratory.

Takekawa said all laboratories on campus undergo annual inspections. The lab where the explosion occurred was last inspected in January and passed muster.

National experts will be involved in the investigation of the explosion.

“Our institute has routinely engaged national experts to review safety procedures,” Taylor said. “And as a result of this incident, HNEI has initiated a comprehensive safety review of all their laboratory operations.”

Meanwhile, the lab where the blast occurred will remain secured indefinitely.

Institute officials could not be reached for comment.

Standing next to the building Thursday morning, Stacy Takeshita, a teaching assistant with the Department of Information and Computer Sciences, said she was on the third floor Wednesday when she heard a loud sound and felt the floor slightly vibrate.

“It was unusually loud,” said Takeshita. “It felt like something huge that dropped on the floor.” She notified her colleagues on the other side of the building, and all safely evacuated.

Faculty and students received an email notifying them of Wednesday’s explosion.

Signs announcing the closure were posted at all of the building’s entrances. Metal and wooden barriers also blocked the entrances.

Sitting on a concrete bench right outside of the building, electrical engineering major Noah Acosta, 21, said he had finished his work in a separate laboratory in the building and left several minutes before the explosion. “Hopefully, she’s OK,” said Acosta of the injured researcher.

Acosta’s friend Brody Asuncion, 22, majoring in mechanical engineering, said he saw Acosta’s Snapchat post of an ambulance and firetrucks at the scene.

“I was kind of shocked,” said Asuncion. The explosion might have been prevented if another person had been in the lab with her, he added.