STAFF and pupils at Morrison's Academy have paid tribute to 15-year-old pupil Anna Johnson who was tragically found dead under a bridge on the M9 close to Bannockburn.

Anna was discovered at around 7am on Tuesday morning by a passing motorist, just half a mile from her home in Stirling. Police investigations are on going with officers looking to hear from anyone who was travelling in this area between 6.15am and 7am, or who may have witnessed the incident.

Tributes have been flooding in for Anna, a fourth year-pupil at Morrison's Academy in Crieff.

The school held an assembly earlier this week to give grief-stricken pupils an opportunity to mourn for their classmate.

Morrison's Academy rector Simon Pengelley said: "Morrison's Academy confirms that it has been informed of the death of one of its pupils by Central Scotland Police.

"This tragic news has come as a shock to all members of the school and our hearts go out to the pupil's family at this dreadful time.

"At present I know a few details but I am sure that you will want to join with me in offering Anna's family our deepest condolences."

Many fellow pupils took to Twitter to express their condolences, one pupil wrote: "School is haunting today. Didn't know Anna but always remember seeing her up in art. Send shivers down my spine."

A school friend also posted: "Was just starting to get to know you as a lovely, beautiful girl. You will be hugely missed at Morrison's."

Another girl tweeted: "I hope you're in a happier place now. My thoughts are with your family and friends. Such a beautiful girl."

And male classmate added: "Can't say I knew her very well but she sat right beside me in Spanish for the past 4 months..disbelief. In gods hands now."

The motorway was closed northbound from the Bannockburn interchange junction on Tuesday, and remained closed for several hours while investigations continued. Police sealed off the overpass at Cambusbarron and erected two tents on the motorway.

Chief Inspector Gordon Dawson said:"We are particularly keen to hear from anybody who may have seen a young woman close to the motorway or on Birkhill Road bridge, in Cambusbarron, which crosses the motorway.

"The motorway is generally quiet at this time of the morning with commuter traffic but busier with heavy good vehicles and we are keen to hear from any driver or operator who had vehicles in the area around this time."

Anyone who has information can contact Central Scotland Police on 01786 456000.

Anna is the second pupil from Morrison's to die on the road in two years. Elli Williams, 16, from Auchterarder, was hit by a car on the southbound carriageway of the road near the town in January 2011 after becoming separated from a group of friends late at night.

A Burns Supper was due to be held at the academy on Saturday evening but the event has been cancelled in the light of Anna's death.