TWO teenage students have been expelled from Blackburn College after being caught smoking cannabis.

And college bosses believe the action has sparked drug-related "revenge" attacks on the building.

Emergency security costing £20,000 has now been installed at the site in a bid to protect the 30,000 students and staff.

The 17-year-old students were excluded on Tuesday, days into their NVQ business courses, after being caught by teaching staff in St Paul's Garden, Blackburn, smoking the Class C drug.

On Monday police arrested a 20-year-old man, not a college pupil, on the site on suspicion of drug dealing. He was detained for drugs searches but was later released.

But college principal Ian Clinton today revealed he has doubled security staff from six to 12, brought in mobile security cameras and extended the alarm system, following two arson attacks. He fears there could be worse to come.

Male toilets in Feilden Street were targeted yesterday and on Tuesday between 10.30am and 11.30am. Fire crews were called and the building was evacuated. In both cases, toilet roll was ignited, filling part of the building with smoke.

"We are not taking any chances," said Mr Clinton.

"Our concern is to protect the students. This is beyond coincidence and we have to conclude the incidents are related and the arsons were a drug-related revenge attack.

"The last thing we want is someone to be hurt and we are working closely with the police." The college has also circulated anti-drugs charity posters reminding students that it is still illegal to smoke the drug despite it being downgraded from a Class B drug earlier this year.

"We take a tough line on drugs as a deterrent," added Mr Clinton. "We treat students with respect but we cannot have them exposed to unacceptable behaviour. At the same time it's not just punitive. If someone wants help for drug-related issues we won't damn them for ever and a day."

A police spokeswoman said: "Two people were arrested on September 9 for possession of cannabis. One was reprimanded and the other released without action. On Monday a patrolling officer was alerted to someone believed to be involved in drug dealing. That man was arrested and detained but, after a drugs search, was released.

"We are also investigating two arson attacks at the college and will be looking to see if they are linked."

One lecturer, who declined to be named, said: "The whole situation is very disturbing."

A level student Peter Smith, 16, said: "When drugs are involved you never know what they will do so it is scary. It's good the college is being strict about security."

Hairdressing student Lisa McDool added: "I am surprised to hear that pupils have been smoking drugs on site. The college is very strict and you can tell things have been stepped up this week."