It has been a tragic story which has led to a huge outpouring of emotion.

Hundreds of people of all ages have read about and commented on the death of Maisie Baxter, 13, who was found at her home at Trowse, near Norwich, on Saturday evening.

The vast majority of people have left heartfelt tributes for the Framingham Earl High School pupil who has been described as a 'sunny, friendly girl'.

But among the poignant messages, so-called RIP trolls – who target tribute websites – left 'horrible' comments and pictures about the teenager, which are now being investigated by officers from the Norfolk police vulnerable people directorate.

The police said that if the Facebook comments were found to be inappropriate they would be looking to take action under the Communications Act 2003.

A children's charity yesterday said those who posted such ghastly messages were the most 'cowardly of cowards' who 'cause as much misery as possible'.

Peter Bradley, deputy director of Kidscape, an anti-bullying and child protection charity, said: 'What the person intends to do is get an emotional reaction and they are successful in that people become very upset and sad and will promote people to put a dialogue on social networking sites for people to comment on.

'They are probably the most cowardly of cowards.

'They are hiding behind what they think is a protective screen and can use their alter egos to cause as much misery as possible.

'A number of people who are internet trolls have a different personality on the internet. You would be surprised who they are and are possibly more passive in real life and more aggressive on the computer.

'It is a huge concern because so many people's lives are ruined by the people on the social networking sites and there is nothing they can do about it.

'They are disempowered because of the trolls' cloak of anonymity. It is very frustrating.'

He added: 'If you can see the trolls making inflammatory comments the best thing is not to react and eventually they will stop.'

In September, Sean Duffy, 25, was jailed for 18 weeks at Reading Magistrates' Court, in Berkshire, after admitting two counts of sending malicious communications relating to Natasha MacBryde, 15.

The teenager died after being hit by a train near her Worcestershire home in February and was one of the victims mocked by Duffy on social networking sites.

On the day after Natasha's death, Duffy posted comments including 'I fell asleep on the track lolz' on the Facebook tribute page created by her brother, James, 17.

Carsten Maple, director of the National Centre for Cyberstalking Research (NCCR) at the University of Bedfordshire, said that even though trolls have been making comments on the internet for some time, the rise of RIP trolls was a new phenomenon that had happened over the past two years.

He believed that RIP trolls are now migrating from Facebook to the microblogging site Twitter because they get a quicker reaction.

Professor Maple said: 'They get some pleasure by causing distress for people.

'It is beyond mischief and it is distasteful. Some people like to see people suffer.

'Because it is on the internet people don't think they can get caught... This is turning into harassment of families.'

Even though he admitted it was difficult to identify these people, he said the police were a lot more aware of the problem and more 'savvy' about digital forensics.

He added that schools should educate their pupils about how to communicate effectively on the internet.

As well as RIP Trolls, the prominence of Twitter and Facebook has led to rise in cases of cyberbullying and racism.

Mr Bradley said: 'Cyberbullying is 24 hours a day seven days a week. You cannot escape from it. It wears people down to the extent that it causes serious damage.

'Once the comments are out there, they are out there forever and these comments will haunt people.'

sophie.wyllie@archant.co.uk