A 15-year-old arsonist has admitted starting a huge blaze that led to fears of toxic fumes in part of north York.

Residents living near a former tannery in Strensall were warned to stay indoors with their doors and windows shut as dozens of firefighters fought a blaze there last spring.

It was the third time in months the disused site in Sheriff Hutton Road had been targeted by arsonists. Residents described it as a "death trap for kids", which had become a magnet for vandals.

The blaze caused thousands of pounds of damage before it was brought under control and extinguished.

Now a 15-year-old from a village to the north of York, who cannot be named for legal reasons, has pleaded guilty to arson on the day he and two other teenagers were due to stand trial. Arson charges against the other two, also from the same area, were dropped at the same time.

York Youth Court adjourned sentence against the 15-year-old until December 19, when he is expected to appear before Selby Youth Court. In the meantime, the city's youth offending team will prepare a pre-sentence report on him.

The teenager was warned that youth justices will consider locking him up when he returns to court.

They could give him a detention and training order of up to two years which would put him behind bars for up to a year, plus up to a year's training and supervised rehabilitation in the community.

The massive fire started on the old tannery's top floor shortly after 6pm on Easter Monday, during the school holidays. Police later revealed three youths were spotted running away from the building.

Thick black smoke billowed down the street and firefighters brought in two aerial platforms to help douse the flames. Crowds gathered to watch two dozen firefighters from Huntington, York and Acomb tackle the blaze.

At one stage, fire chiefs feared people living nearby may have to be evacuated for their own safety, but did allow local residents to remain. However, they warned the blaze could start toxic fumes spreading through the area and issued the warning to keep doors and windows shut.

The fire burned a huge hole in the tannery roof and completely destroyed much of the third floor.

The building had been disused for about a year before the blaze.

Updated: 10:11 Friday, November 25, 2005