Former BBC Radio 2 presenter Scott Mills was questioned by police over allegations of serious sexual offences against a teenage boy under 16 in 2018, but the case was dropped due to a lack of evidence.
The breakfast show host was abruptly taken off air last week before his sacking over allegations related to his "personal conduct" was announced.
The 53-year-old last presented the programme one week ago - on Tuesday 24 March - and signed off with: "See you tomorrow".
The claims relate to when Mills was working at BBC Radio 1, and it is not known if the corporation was told of the investigation at the time.
It is also not clear if his sacking is related to the police investigation.
London's Metropolitan Police said that a man, who was in his 40s at the time of the interview, was investigated in 2016 over allegations of serious sexual offences that took place between 1997 and 2000.
They questioned him under caution in July 2018.
Mills was not charged with a criminal offence and the case was closed due to a lack of evidence.
Police do not identify people who are subject to an investigation before any charges are brought.
A spokesperson said: "In December 2016, the Met began an investigation following a referral from another police force.
"The investigation related to allegations of serious sexual offences against a teenage boy. These were reported to have taken place between 1997 and 2000.
"As part of these inquiries, a man who was in his 40s at the time of the interview was questioned by police under caution in July 2018.
"A full file of evidence was submitted to the Crown Prosecution Service, who determined the evidential threshold had not been met to bring charges.
"Following this advice, the investigation was closed in May 2019."
Police confirmed that the boy was under 16.
News of Mills's sacking led yesterday's 12pm bulletin on his former station, BBC Radio 2.
The broadcaster issued a news alert today reporting the closed police investigation.
In an email sent to staff, BBC Director of Music Lorna Clarke wrote: "I wanted to personally let you know that Scott Mills has left the breakfast show, and the BBC.
"I know that this news will be sudden and unexpected, and therefore must come as a shock.
"Not least as so many of us have worked with Scott over a great many years, across a broad range of our programmes on R1, 5Live, R2 and TV.
"I felt it was important to share this news with you at the earliest opportunity.
"Of course, it will also come as a shock to our audience and loyal breakfast show listeners too. I will update everyone with more information on plans for the show when I’m able to.
"While I appreciate many of you will have questions, I hope you can understand that I am not going to be saying anything further now."
Mills has been contacted for comment.
The BBC said it would not comment beyond an earlier statement: "While we do not comment on matters relating to individuals, we can confirm Scott Mills is no longer contracted to work with the BBC."
Source: Press Association
