At least 22 people were killed and 59 more were wounded Monday evening in an explosion at the Manchester Arena following a concert by singer Ariana Grande, BNO News reports.

The incident happened at just after 10:30 p.m. local time. People in the area said they heard a loud "bang".

Local police tweeted that they had responded to a “serious incident” at Manchester Arena and added that there were “fatalities and injuries” in the explosion.

“Emergency services responding to serious incident at Manchester Arena. Avoid the area. More details will follow as soon as available,” the tweet read.

The cause of the explosion is not yet clear, but North West Counter Terrorism unit is treating it as a possible terrorist incident, sources told the BBC.

Network Rail said train lines out of Manchester Victoria station, which is close to the concert venue, were blocked.

Footage from the scene disseminated on social media showed people fleeing Manchester Arena following the incident:

An eyewitness told Sky News, "I and my sister, along with a lot of others were seeing Ariana Grande perform at Manchester Arena, and we were all exiting the venue when around 10:40-10:45 p.m.-ish a huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the arena.”

"It was one bang and essentially everyone from the other side of the arena where the bang was heard from suddenly came running towards us,” said the eyewitness.