Hassan's court appearance came amid claims that the mother of a Syrian refugee who was held over the bombing but then released had suffered a heart attack after hearing of her son's arrest.
Yahyah Farroukh, 21, who was was released without charge on Thursday, was seized by police last weekend outside Aladdins Fried Chicken, in Hounslow, west London, where he worked.
Today his boss at the takeaway, Suleman Sarwar, demanded an apology from the police and said his mother was in a critical condition in a hospital in Egypt after collapsing from shock.
Mr Sarwar said the takeaway had received "abuse, threats, anger, and hatred" after Mr Farroukh was labelled "a terrorist to the world".
Speaking about the Parsons Green attack, Metropolitan Police Commissioner Cressida Dick said on Friday that the partially-detonated bomb was "packed with shrapnel".
Ms Dick added: "Thank goodness nobody was killed at Parsons Green. It must have been absolutely horrific for the people in the train.
"It could have been so much worse."
Police continue to question three other people, including a 17-year-old boy, in connection with the rush-hour bombing, while a 48-year-old man arrested in Newport, south Wales, on Wednesday was released without charge.
The teenager was detained after officers raided what neighbours described as a "halfway house" in Thornton Heath, south London, at around 12.05am on Thursday.
The investigation into the attack, which injured 30 people, has also seen two men aged 25 and 30 detained in Newport.
Hassan, who lived in Sunbury with a couple who have fostered dozens of children over the years, was detained at the Port of Dover last weekend.
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