Two teenage girls who were believed to have been raped and hanged by their attackers actually committed suicide, according to India's top federal investigating agency.

The Central Bureau of Investigation (CBI) told the Hindustan Times newspaper that the local police probe was conducted "erroneously".

Six months ago, pictures of the girls' bodies hanging from a tree in their home village of Katra, in Uttar Pradesh state, shocked a country long inured to violence against women.

Local police said at the time that the girls had been gang-raped and murdered. Five men were arrested but later freed on bail.

The CBI is scheduled to hold a news conference with more details later.