Nathan Matthews, 28, and Shauna Phillips, 21, are reportedly being held by police over the Watts' murder, but police must either charge or release them by this afternoon.
Police investigating large-scale fraud linked to extremists travelling to Syria have arrested two men in London on suspicion of money laundering.
Scotland Yard said the arrests are linked to reports of vulnerable and elderly victims being "cold called" over the phone by a suspect impersonating a police officer, who informs them their bank account has been compromised.
Victims are then tricked into transferring money to an account under the control of the suspect, with one elderly victim losing around £150,000.
The two men, aged 23 and 29, were arrested at addresses in west and east London.
They remain in custody at a police station in south London.
This footage may embarass Prince William, who was in China to fight against the illegal wildlife trade and protect elephants.
But in the same animal sanctuary he visited, but unseen by him, one area is said to house elephants which are made to perform for visitors' amusement.
There are allegations of mistreatment in the training process, in which the animals are made to spin and play football.
ITV News' Royal Editor Tim Ewart reports:
There were emotional scenes today as Becky Watts' family laid flowers at her house, where she was last seen alive.
Police only have a few hours left to either charge or release Becky's stepbrother Nathan Matthews and his girlfriend Shauna Phillips, who are reportedly being held over her murder.
ITV News Correspondent Rupert Evelyn reports from Bristol:
Police have been given an extra 24 hours to question five suspects arrested in connection with the Becky Watts case.
The four men and one woman, aged between 23 and 29, were detained on Monday on suspicion of assisting an offender.
Officers have until this afternoon to question two murder suspects in the case, who are reported as being Becky's stepbrother Nathan Matthews and his girlfriend Shauna Phillips.
The Lib Dems and Sir Richard Branson are calling for drug addiction to be treated as a health problem rather than a crime.
The devastated family of ex-Royal Marine Konstandinos Erik Scurfield, killed in Syria fighting Islamic State militants, have paid tribute to the soldier.
In a statement, they said: