Students at Cliff Park High School in Gorleston were sent home just after 1200 GMT.

Although the source of the leak was not immediately known, headteacher Bob Bond said he was confident classes would be back to normal on Tuesday.

He said the danger had been spotted when a member of staff noticed the smell of gas in a classroom.

Sent home

Mr Bond said: "When we went down there it was very clear that there was a smell of gas, so we took all the necessary precautions.

"We phoned Transco for advice and they advised evacuating the building straight away, which we did.

"Given that we knew checks would take some time, we didn't feel we had any choice but to send students home.

"I predict confidently that we'll be in school tomorrow as normal."

Transco workers spent all afternoon at the school to deal with the problem.