18-year-olds, Katie Gee and Kistie Trup, were working as volunteer teachers in the country, and they are now on their way to the United Kingdom.
The British foreign officer released a statement condemning the incident, whilst noting that that it was "concerned to hear of an attack on two British nationals."
Whilst the women's mothers, Nicky Gee and Rochelle Trup, said in a statement, "Both families are extremely upset and distressed at this completely unprovoked attack on their lovely daughters who had only gone to Zanzibar with good intention." Nicky Gee also added that all of her daughter's face and body had been burned in the attack.
Police have confirmed that whilst the women walked through the streets of Stone Town, two men on a moped drove up alongside them and then threw the acid onto them.
Mkdama Khamis, the deputy police commissioner, told AFP news agency, "The motive for the attack on the volunteers aged 18 years, has not been established. Investigations are on until we apprehend the criminals."
The Daily Mirror has since speculated that pair were attacked for singing in the streets during Ramadan. On July 24, Kate Gee tweeted, "A Muslim woman just hit me in the street for singing on Ramadan. Is that normal?"
Oli Cohen, 21-year-old friend Katie Gee, told the paper, "Katie was attacked two weeks ago by a Muslim for singing on Ramadan. She was shocked as it just came from out of the blue, but she wasn't scared enough to come home she stayed out there to finish her trip and volunteering."
The pair's injuries aren't life threatening. In November there was another acid attack in the country, whilst two Catholic priests were shot dead in February and December respectively.