NBC News is reporting at least 22 people were killed and some 60 others seriously injured as an explosion — reportedly the work of a suicide bomber — rocked the Manchester Arena in Manchester, England on Monday evening as an Ariana Grande concert was ending. Emergency crews rushed to the scene after blasts, which were first reported about 10:40pm London time (5:40pm ET).

As TMZ reported, Grande had just left the stage when an explosive device detonated in the rotunda area near the front door as people were leaving the concert. Grande was not injured. Multiple U.S. officials briefed on the investigation so far said preliminary reports indicate that a single explosion took place outside the arena on the southwest side opposite the Manchester Victoria transit station, which is part of the greater arena complex. The explosion occurred as the concert ended, catching people as they exited. British and U.S. law enforcement sources told NBC News that at least 20 people had been killed but that the information was preliminary and subject to change. Greater Manchester Police said that there were “a number of confirmed fatalities and injuries” as hundreds of fans fled the arena, which sits atop the Manchester Victoria transit station. British Transport Police said all lines to Manchester Victoria were closed, and Northern Railway said the station had been evacuated.

A label rep told Variety that Grande was “okay,” but TMZ said Grande was inconsolable and “in hysterics” after learning of the deaths and injuries. For her part, Grande tweeted, ” broken. from the bottom of my heart, i am so so sorry. i don’t have words.” TMZ also reports that Grande’s next concert — which scheduled for Thursday at London’s O2 Arena — is now up in the air.