The suspect, believed to be Jo’s neighbour Vincent Tabak, was arrested on Thursday morning.
Detectives have been granted a further 12 hours to question him and will then have to apply to magistrates for a further extension.
Meanwhile, tarpaulin continues to be up around the flats of Jo and Dutch architectural engineer Vincent Tabak.
Workmen from D.R.A Maintenance Ltd yesterday put poles and green tarpaulin around Jo’s basement flat and Flat 2 of 44 Canynge Road, which also overlooks the garden.
Forensic officers were also searching a flat where a friend of Vincent Tabak lives.
Officers also cordoned off the Victorian townhouse at 37 Aberdeen Road in Clifton – which is one mile from Canynge Road – at around 12.30pm yesterday.