Jansson, 23, from Trollhättan on Sweden's west coast, was last spotted on April 12th at 9:30 in the morning on Ilford high road, greater London.
She had been living in shared accommodation in the Ilford area for the last few months after moving to England to find work. Scotland Yard are treating her disappearance seriously, while family and friends have gone to London to aid with the search.
"We do not know what happened but we are treating it as a high-risk disappearance," a spokesperson for the Metropolitan Police told Aftonbladet.
Attempts to track down the Swede, also known by her middle-name Marie, have so far proved futile. The police have checked CCTV cameras and monitored activity on Jansson's debit card but have not managed to establish any credible leads.
"We have no idea what happened, her brother and I are in London to be nearby and to be able to help the police," the missing girl's father Staffan told Aftonbladet.
Jansson was last seen wearing a dark grey coat, a flowery blouse and jeans.
Anybody with information is urged to get in contact with the Metropolitan Police.