India, Oct. 16 -- Over two years and hundreds of hoax bomb threats to schools later, Delhi Police has cracked just one case, and experts, principals and parents are losing patience with a force that has yet to find an answer.

The latest threats came on Thursday morning, when at least six Delhi schools, including The British School, Mount Carmel, and Ahlcon Public School received emails warning of bombs on their premises. Bomb squads searched the schools after the emails came in around 9am, and the threats were declared a hoax - the same drill Delhi's schools have been through hundreds of times in two years, with only one hoax perpetrator ever caught.

Experts and parents now want police to stop treating each email as a separate incident ...