London transport authorities say they have re-opened the station where a bomb partially detonated on a Tube train, injuring 29 people.

The blast sent what witnesses described as a fireball through the packed train during the Friday morning rush hour. The injuries, some from the explosion and others from an ensuing stampede, where not thought to be life-threatening.

Transport for London said that the Parsons Green station in southwest London station had reopened at 1:30 am on Saturday, more than 17 hours after the explosion.

British authorities increased the country's terror threat level to "critical," meaning they think another attack may be imminent. No arrests have been made and a major manhunt for suspects is underway. British soldiers are being deployed across the country at public sites to assist police.

Police are searching for suspects in the London subway blast that injured more than two dozen people as hundreds of soldiers are being deployed across the country.

Authorities increased the terrorism threat level to "critical" late Friday, after a bomb partially exploded during the morning rush hour, meaning a government task force believes another attack may be imminent.

The soldiers will add to the police presence Saturday at public places to deter attacks after the blast on a District Line train. No arrests have been made. The explosion and an ensuing stampede at Parsons Green station injured 29 people. None of the injuries, some of them burns, were believed to be life-threatening.

The bomb was put into a bucket and concealed in a shopping bag.

Parsons Green terror attack
Parsons Green station reopened less than 24 hours after the explosionReuters