Staff have been briefed to keep an eye out for symptoms resurfacing at a college where students were hit by a mystery illness.

Teenagers returned to Energy Coast UTC University Technical College at Lillyhall, Workington, for their first day of classes yesterday since an evacuation last week.

Principal Gary Jones, said he was delighted things were back to normal following the alert, believed to have been sparked by a mystery virus.

He said the fact students were off the site for three days would have reduced the chance of any condition spreading.

But he added: "We will be monitoring the situation."

Last week the building was evacuated following fears of possible contamination, with the 360 people who were inside leaving within four minutes.

Mr Jones praised the way his students handled the evacuation and pointed out it was the kind of situation they may face in their engineering careers.

The alarm was raised last Thursday after two students – both of them male – passed out.

Another was taken ill and several more were affected by dizziness and headaches.

It is thought now that these symptoms were caused by a mystery virus.

Police were called to the building just after 2pm, along with fire service personnel and paramedics.

One student was taken to the West Cumberland Hospital in Whitehaven for treatment but was later discharged.

The college remained closed on Friday.

Engineers checked out heating and air conditioning equipment and other staff carried out a "deep clean" of the building.

Mr Jones said: "We are 100 per cent back into lessons and normal activities."

He said many of the students wanted to go onto careers in the nuclear industry and this was a good example of an emergency response.

He added: "They have all got aspirations to work in engineering environments, but this isn’t the way I wanted to test our response plan."