Authorities in Shanghai Baoshan District are planning to install sensors on 12,000 manhole covers that will allow them to be monitored by satellite, a local official said yesterday.

The sensors will be able to detect if the covers are removed or if there is a gas or water leak in the tunnel below, said Chen Dawu, the person in charge of the project.

Shanghai has about 6.5 million manholes and thousands of covers go missing every year.

“Open manholes are a safety hazard, but with 19 different agencies responsible for them, getting covers replaced can be a lengthy process,” Chen said.

“The satellite system will help us to identify who should take charge in the event of a problem or a cover going,” he said.

The theft of manhole covers is such a problem that the city government has begun installing safety nets inside the holes to prevent people falling into the tunnels below.

As well as helping to keep people safe, the new system will sense for leaks from water pipes and gas lines, many of which are very old, the official said.

Chen did not say when the new sensor system will be introduced or how much it will cost, but said that if the trials are successful, it will be rolled out across Shanghai.