A social networking site where comments were posted to a 14-year-old girl who later died after "web bullying" says it will help the police investigation.
Hannah Smith, from Leicestershire, was found hanged on Friday.
Ask.fm allows users to post anonymously and Hannah's father Dave Smith said he found posts on his daughter's page telling her to die.
In a statement, ask.fm said its moderators "ensure genuine concerns are acted upon immediately".
'In-site reporting button'
The Latvian-based company said: "Hannah Smith's death is a tragedy; we would like to convey our deepest condolences to her family and friends.
"We have reached out to Leicestershire police and would be happy to co-operate with their investigation into the circumstances.
"Ask.fm actively encourages our users and their parents to report any incidences of bullying, either by using the in-site reporting button, or via our contact page.
"All reports are read by our team of moderators to ensure that genuine concerns are heard and acted upon immediately - and we always remove content reported to us that violates our terms of service."
The apology follows a message written on Facebook by Hannah's father, Dave, that he found bullying posts on his daughter's ask.fm page from people telling her to die.
Mr Smith wrote: "Just to let all my friends know my youngest daughter took her own life last night.
"My heart is broken in 2 and is gonna take a long time to repair i just hope that none of you have to go through the pain im goin through rite now [sic]."
Mr Smith has called for tighter controls to be applied to social networking sites such as ask.fm.
He wrote: "I have just seen the abuse my daughter got from people on ask fm and the fact that these people can be annoymous is wrong [sic]."
On a Facebook page set up in memory of his daughter, he asked people to sign an e-petition to introduce safeguarding measures on sites used by children.
The page now has nearly 45,000 "likes".
The petition states: "Please sign if you would like the Government to step in and insist that Ask.fm and similar sites help us protect our young people. They are able to join from the age of 13 and can post anonymously."