This is sadly a story that that used to be common among areas that had an influx of people from areas of Pakistan or India, Leicester being one of those areas.
It happens less so or is reported less so over the last few years but a few gas explosions have occurred and reported as various faulty reasons.
In the past it has been down to ignorance and out of date portable heaters, some using liquid fuels like paraffin.
Some are suspected to have been deliberate attempts to by pass gas meters, some are due to tinkering with the building without proper knowledge or planning permission and some rumours would say it could imbecile elements trying to make IED with stored chemicals etc
This is highly likely to be a case of work out, corroded, or tinkered with pipework