The bodies of Davina Baker, 16, and her sister, Jasmine, 13, were found on Wednesday morning at their mother's home in Stretham, near Newmarket. Police sources said they died from stab wounds.

Their mother, Rekha Kumari-Baker, 39, is being questioned on suspicion of their murder.

A Cambridgeshire Police spokeswoman confirmed on Thursday that, as part of their inquiry, officers were looking into the content of websites used by the sisters.

"Officers will today, as part of their detailed investigation into the girls' background, be looking into internet sites, including Bebo, that were used by the girls," she said. "They will be investigating what has been said on them and what various people have been posting."

The sisters both had personal pages on the Bebo website.

Detectives have also spoken to social workers and education officials as part of the probe.

A Cambridgeshire County Council spokesman said Davina was known to social services.

"Social services did have contact with the older girl regarding behavioural problems at school," he said. "Social services and education staff at the county council have met with the police as part of their ongoing investigation."

Police said a post-mortem examination on the bodies of the two girls is likely to be completed on Thursday night.