Eilidh MacLeod is still missing after Monday's bombing.
Third Teen Arrested Over 'Hoax Bomb Calls'
A third teenager has been arrested in connection with hoax bomb calls to schools.
Threats were made to schools in Clydebank and Lanarkshire last week, police said.
A 15-year-old boy from Glasgow was arrested on Wednesday over the incidents and is expected to appear at Glasgow Sheriff Court on Thursday.
He is the third teenager arrested this month in connection with hoax bomb threats to schools.
A 16-year-old was arrested over alleged threats to Cumnock Academy and Auchinleck Academy in East Ayrshire on Wednesday June 1.
A 15-year-old boy was arrested on June 2 following incidents in Glasgow, Clydebank, Campbeltown and Lanarkshire.
A force spokesman said: "Police Scotland takes hoax calls extremely seriously.
"They divert police resources, cause disruption and alarm to the public.''
There will be extra body search, ticket checks and bag restrictions.
Army personnel will be stationed at 12 military and civil nuclear sites in Scotland.
Police say the shopkeeper has been left badly shaken.
Most Viewed Pictures On Heart
Recently Played Tracks
To listen live, choose your preferred station:
Now playing: The best feel good music
Deposit £10 to get a £40 Welcome Bonus - That's £50 to play bingo, slots and more!*
Over 50 tracks to make you feel-good. New album out now...
Find your local four day weather report here.
Make Heart the soundtrack to your day and you could be a winner with great prizes up for grabs throughout the day.
Find out more about some of the companies advertising on Heart Scotland- East.