President Enrique Pe?a Nieto of Mexico was caught in a fresh storm on Sunday over claims that his personal residence is owned by a company linked to a Mexican member of the Chinese-led consortium that won a high-speed rail contract last week – only to be stripped of it days later.

The allegations, based on documents seen by the Financial Times and reported on the Aristegui Noticias news website, added fuel to protests over the disappearance of 43 students, who were arrested by police and are now feared dead.

The presidency said in a statement that the first lady, Angélica Rivera, had signed a contract with Ingeniería Inmobiliaria del Centro (IIC), a company owned by the businessman Juan Armando Hinojosa, in January 2012, to purchase two properties. The properties, adjacent to one she already owned, were originally bought by IIC, and the family’s residence was built on the land they once occupied.