Seven teenage boys involved in throwing a gas canister on to a freight line - a day after the Selby rail crash which killed 13 people - were ordered to undergo lessons in rail safety.

The boys aged from 13 to 15, from Skipton, placed the two foot tall, 13kg canister on the line where trains, carrying thousands of tons of aggregate, travel between Skipton and Swindon quarry near Threshfield.

A police officer snatched the cylinder from the line under the bridge near Upper Sackville Street, Skipton, after being notified a train was on its way, Skipton magistrates were told.

A 15 year-old boy from Skipton, who admitted maliciously placing the canister on the line with intent to obstruct, overthrow or destroy any engine, was sentenced to undergo 18 hours' reparation supervised by the Skipton youth offending team.

The six other youths, aged 13 and 14, five from Skipton and one from Lancashire, were ordered to carry out 12 hours' reparation after admitting the lesser offence of obstructing the railway.

They will have to meet British Transport Police and railway officials to be instructed about rail safety.

And they will face lessons on the consequences of what damage and distress their actions could have caused.

Their parents were given parental bindovers in the sum of £100 for 12 months.

The incident happened the day after the Selby rail disaster on February 28 in which a Land Rover towing a trailer careered onto the London to Newcastle line, derailing two trains and killing 13 people.

John Mewies, one of the three defending solicitors, criticised Railtrack for failing to ensure the Skipton line was safely fenced off. And he claimed there were no signs warning of the danger of going on the line.

Prosecutor, Claire Murden said all the boys in one way or another were involved in placing the canister on the line.

A Railtrack spokesman said: "Railway crime is something that Railtrack and our industry partners will not tolerate."