Dhaka, June 4 -- The police have failed to solve the mystery behind the cutting of the secure red telephone line of the Prime Minister's Office at the Secretariat, the administrative heart of Bangladesh, three days after the incident came to light.

Several agencies have joined the investigation, but no breakthrough has emerged, bdnews24.com reports.

Dhaka Metropolitan Police Detective Branch chief, Additional Commissioner Shafiqul Islam, said on Thursday: "We are carrying out a shadow investigation. Other agencies are also investigating. There has been no progress worth reporting so far."

The government's seven-day Eid ul-Azha holiday began on May 25. When staff returned to the secretariat on Monday after the break, they found the red ...