Journalist Amelia Hill, who has been covering the phone hacking scandal for The Guardian, has been questioned by detectives over alleged leaks from police.
Hill is the special investigations correspondent at The Guardian.
She was contacted and questioned by police following the arrest of a detective by his own force last month.
A Guardian News and Media spokeswoman said: "We can confirm Amelia Hill has been questioned in connection with an investigation into alleged leaks.
"On a broader point, journalists would no doubt be concerned if the police sought to criminalise conversations between off-record sources and reporters."
Earlier today, a 35-year-old man was arrested as part of the investigation into phone tapping at The News of the World.
Officers from Scotland Yard's Operation Weeting held the man in a pre-dawn swoop on his home.
He was taken to a north London police station for questioning on suspicion of conspiracy to intercept voicemail messages.
The man, who has not been named, was held by police at 5.55am.
He is the 16th suspect arrested on suspicion of phone hacking since Weeting, Scotland Yard's fresh investigation into the illegal interception of voicemails, was launched in January.
A series of high-profile figures have been held for questioning, including former News International chief executive Rebekah
Brooks and ex-Downing Street communications chief Andy Coulson.
The scandal has already led to the closure of the News of the World after 168 years and the resignation of Metropolitan Police Commissioner Sir Paul Stephenson and Assistant Commissioner John Yates.