US President Donald Trump's comments in the wake of Friday's London tube bombing were unhelpful, Britain's Home Secretary says.
The two arrests indicate authorities believe the attack at the Parsons Green station was part of a coordinated plot, not the act of a single person.
"Following the attack on Parsons Green last Friday, the police have made good progress with what is an ongoing operation", she said on Sunday.
Her comments come after an 18-year-old man was arrested on Saturday in the departure lounge of Dover port in connection with the blast.More news: Seoul, US agree on 'stronger, more practical' pressure on Pyongyang
The 21-year-old was detained in Hounslow, west London at around 11.50pm on Saturday.
Twenty-nine people were injured when an improvised explosive device partially detonated on a London tube train in Parsons Green station on Friday morning.
Some passengers suffered burns and others were hurt in a stampede to escape.
Police said they are searching a residential address in Stanwell, Surrey, in conjunction with this arrest.More news: Is there a Bearish outlook for Marvell Technology Group Ltd
Police are continuing to search a foster home in Sunbury-on-Thames, Surrey, in connection with the teenager's arrest on Saturday.
Interior minister Amber Rudd said on Sunday the second arrest indicated it was not a "lone wolf" attack, but there was no evidence IS was involved.
Rudd's comments echoed those of British Prime Minister Theresa May, who on Friday said it was not helpful for anyone to speculate on investigations.
This means an attack may be imminent, as soldiers and armed police have been deployed to secure strategic sites and hunt down the perpetrators.More news: Arsene Wenger: Alexis Sanchez 'well loved' at Arsenal and 'happy'
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