Explosion rocks Harvard Medical School building

Officials are looking for two people, they said set off an explosion inside a Harvard Medical School building.

Boston25News reported that the blast at the Goldenson Building occurred around 2:48 a.m. on Saturday.

A police officer said they saw two people running from the building and tried to stop them, but then the officer ran into the building, going to a floor where a fire alarm had been set off.

Images from surveillance video showed the people wearing masks, and that the explosion was intentional, CNN reported.

There was no structural damage to the building and officials said there was no ongoing safety threat, so the facility reopened.

No explosives were found in the building and officials are still trying to figure out what went off and why.

No one was hurt in the blast, the university said in a statement. School officials said the explosion happened in a small section of the fourth-floor hallway.

Harvard University Police and the FBI are investigating.