Police involved in the arrest of ‘Lostprophets’ vocalist Ian Watkins, in relation to an alleged plot to rape a baby, are under investigation over whether or not they acted quickly enough.
The Independent Police Complaints Commission (IPCC) is looking at whether South Wales Police "failed to take appropriate and timely action" over information received about the singer.
The 35-year-old, whose band have sold more than 3.5 million records worldwide, was arrested in December with two women.
He is accused of conspiring to rape a child under the age of 13 and five other sex abuse charges.
IPCC commissioner for Wales Tom Davies said: "We received a referral from South Wales Police on January 25, 2013 relating to Ian Watkins.
"Following a thorough assessment I have decided that we will carry out an independent investigation.
"Our investigation will determine whether or not South Wales Police failed to take appropriate and timely action in relation to information they were in receipt of in advance of Mr Watkins's subsequent arrest.
"We are aware of four forces having provided South Wales Police with information but, as criminal proceedings are active, it would be inappropriate to publish further information at this time."
South Wales police referred themselves to the IPCC over the case.
Mr Watkins, 35, is charged with conspiracy to engage in sexual activity with a child under 13 and four offences relating to possession and distribution of indecent images of children.
The alleged offences date from May to December 2012.
Watkins is due to appear at Cardiff Crown Court for a plea and case management hearing on March 11.
He is accused alongside two women aged 20 and 24, from Doncaster and Bedford respectively, who cannot be named for legal reasons.