The 20-year-old British student who died of cardiac arrest after being given a lethal injection of silicone, was under surveillance by federal drug agents at the time of her death.

According to London’s Daily Mail newspaper, Claudia Aderotimi and her three friends were “flagged” by immigration officials during a previous trip from London to Philadelphia where they had butt and hip enhancement procedures.

Miss Aderotimi and her friends came under surveillance soon after they checked into the £100-a-night hotel near Philadelphia airport by agents who had received a tip-off that the girls were allegedly involved in some kind of drugs activity.

Officers from the Customs and Immigration Service sat outside her hotel unaware that in her fourth-floor room, she was being given a fatal silicone injection.

Police have named the woman suspected of administering the dose as a transgender singer who calls herself ‘Black Madam’.

The 41-year-old is being hunted by police after they seized syringes and silicone from her home.

Multiple ID cards in different names, among them Vanessa Brown and Padge Windslowe, were also found.