A fire broke out at 12:46 p.m. yesterday in the University of Massachusetts Lederle Graduate Research Center Tower, causing the building to lose power and possibly remain closed for several days.

The fire was caused by electrical arcing in the main electrical room of Tower B. According to the Amherst Fire Department, the fire had self-extinguished by the time the first crews arrived at the scene.

Two electricians had been working in the room prior to the fire, AFD said. Both suffered mild smoke inhalation, according to multiple sources, including AFD and Patrick Callahan of the UMass News Office.

According to the AFD also said the electricians complained of minor burns. The workers were examined by paramedics and refused transport to area hospitals.

About 10 students were trapped in elevator two on the 15th floor, due to the power loss. With the help of elevator technicians already on the scene, the occupants were freed, said the AFD.

About 37 firefighters, four pumpers, the ladder truck, three support vehicles, two ambulances and a chief officer responded to the incident.

One firefighter said he had difficulty breathing and was transported to Cooley Dickenson Hospital. He was treated and later released.

UMass police officers quickly arrived at the building to control the accumulating crowd of onlookers. The police precautions included stringing caution tape around the area, deploying two mounted patrol officers and at least one officer on a bicycle.

According to Callahan, the arc damaged power delivery within the building. The Physical Plant then shut off power to the main switch of the building, and has been working on bypassing the problem area, he said.

Environmental Health and Safety initiated a plan at around 2:15 p.m. to save experimentation that could be lost during the power outage. Researchers were instructed to move to the second floor of the Lederle low-rise and wait to be escorted in small groups to their offices in the tower.

At 2:50 p.m., 44 people waited in the low-rise to return to their research. They expressed concerns about shutting down their experiments or getting them on back-up power.

Peter A. Bryngelson, a doctoral chemistry student, said that without electricity to power his freezer, a sample he has worked on for about a week could go bad.

“Then again, there’s months of work and years of work in the freezers,” he said.

“They contain our life’s work,” said Associate Professor Jennifer Normanly.

Normanly, who works in the biochemistry and molecular biology departments, said researchers are prepared for this kind of incident. For them, the difficulty was getting back into the building to plug their equipment into backup batteries.

According to Bryngelson, the coldest freezers, which refrigerate at negative 80 degrees Celsius, can hold the work at sufficient temperatures for about five to six hours without electricity.

UMPD officers and Emergency Health Services officials coordinated escorts, who guided researchers to their offices in the dark. This process began at 3 p.m. First, those in charge went over a list of freezers they knew to be critical to the preservation of research. The list, which was from a planned shutdown of the tower almost two years ago, had to be updated before it could be used to assist those managing the effort.

The reentry was a slow process for both officials and researchers, who waited for several hours as they were called by floor to return to their equipment. Within the first hour, only the five highest floors had been entered.

Those in charge of the process urged people to go home if they did not need to tend to equipment critical to their experiments.

Several students questioned police officers about the reopening of the building and expressed concern for missing their courses.

Multiple sources confirmed that the tower will remain closed for at least an entire day. One official coordinating the reentry announced that the building may be closed for several days. The closing does not include the low-rise building.

The town’s electrical inspector is working with the University to further investigate the cause of the electrical arcing, which is still unknown, said the AFD.

No estimate of the damage caused to the building was available at press time.

For more information visit www.umass.edu/closing.