Police who arrested Lost Prophets singer Ian Watkins over an alleged plot to rape a baby are under investigation over whether they acted quickly enough.
The police watchdog is looking at whether South Wales Police "failed to take appropriate and timely action" over information received about the 35-year-old vocalist.
Watkins, 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.
The Independent Police Complaints Commission (IPCC)'s 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."
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.