A former aide to ousted Malaysian prime minister Najib Razak has been arrested in connection with the probe into scandal-hit state fund 1MDB, according to local media.

The arrest is the first detention in a renewed probe into the disappearance of billions of dollars from 1MDB. It comes a week after Mahathir Mohamad, the prime minister, said the authorities had built an “almost perfect case” against his predecessor, who set up the 1MDB state investment fund in 2009.

Malaysia’s anti-corruption commission secured an order from the Putrajaya magistrates' court for a 42-year-old man to be remanded for seven days, starting on Monday, national newswire Bernama said. The former aide will help in investigations relating to 1MDB, from which $4.5bn has allegedly gone missing, Bernama said.