Police have closed their investigation into an alleged sexual assault by a man on a 13-year-old boy on a bus.

The incident is said to have happened on Saturday, June 8 when a boy was boarding a bus from his home in Great Yarmouth to meet his friends in Norwich.

He sat upstairs on the X11 First Bus and was the only person on the top deck until a man got on and is said to have sat next to the boy.

The man is then reported to have continually touched the boy's leg inside his thigh and even attempted to kiss the boy before he exited the bus at Acle.

READ MORE: Community reveal horror at seeing man killed outside their front doors

READ MORE: 'Disgusting' public toilet row turns foul with people urinating on street

The boy remained on the bus to see his friends in Norwich.

His mum said he was left petrified after the incident and did not report it until three weeks after it happened when he told a teacher at his school.

The Great Yarmouth bus to Norwich terminates at Norwich Bus Station, pictured by Denise BradleyThe Great Yarmouth bus to Norwich terminates at Norwich Bus Station, pictured by Denise Bradley (Image: Denise Bradley)

As soon as the boy's mother was told she immediately reported it to the police and she says she is unhappy with how the police have dealt with the incident.

But now a Norfolk police spokeswoman has said their investigations into the incident have been closed.

A statement read: "All lines of enquiry have been exhausted and the case has been closed.

"Of course, we would always review any new information provided to us."

First Bus had been approached for comment.