London—the BBC reports that 22 people were injured after an “improvised explosive device” detonated earlier this morning at a commuter train station in southwest London. No deaths or life-threatening injuries have been reported.

The blast went off at 8:20 am (3:20 am ET) at the Parsons Green tube station during rush hour.

Witnesses describe the explosion as a fireball coming from a bag. Gustavo Vierra, an eyewitness to the event, told CNN: “Suddenly, there was this boom. Everyone shouting and screaming... We were just leaving the carriage [when the explosion happened]... Just heard and everyone starting running... And I didn't look back.”

Act of terrorism; suspect unknown

Police are treating this as an act of terrorism.

As of yet, police don’t know who perpetrated the crime. The Metropolitan Police’s assistant commissioner Mark Rowley hasn’t said whether any arrests have been made.

SO15, Scotland Yard’s counter-terrorism division, has taken the lead with the investigation.

It appears the IED partially failed and didn’t detonate properly. According to BBC security correspondent Frank Gardner, it could have been “far worse.”

This is the fifth major terrorist attack in London this year. London has been placed on critical alert, meaning that another terrorist attack is expected and imminent.

Leaders issue their support

British Prime Minister Theresa May issued a statement saying, “My thoughts are with those injured at Parsons Green and emergency services who are responding bravely to this terrorist incident.”

US President Donald Trump also tweeted his support this morning, saying, “Another attack in London by a loser terrorist!

London Mayor Sadiq Khan says that there will be a larger police presence over the weekend.

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He released a statement on Facebook concerning the attacks, saying, “As London has proven again and again, we will never be intimidated or defeated by terrorism.”

Local support for victims of attack

Local restaurants are handing out food to the victims.

Stephen Cowan, leader of the London Borough of Hammersmith and Fulham told the BBC that London “is an amazing place to live.”

When asked by the BBC's Barry Caffrey about advice he would give to local residents concerned about their safety, he replied, “Live the life you want to live. Don’t let any terrorist or bully knock you off that.”

We’re not going to be cowed by cowards,” he added.