Experiments show that robotic vacuums can move electric heaters. (Provided by the Tokyo Fire Department)

Robotic vacuums can keep your home dirt-free, but Tokyo firefighters are warning that they could cause a fire by knocking electric heaters.

The Tokyo Fire Department said two such fires have been reported this winter in the metropolis.

Officials said on-site inspections, interviews with residents and experiments corroborate the danger of the devices, although no injuries were reported.

“People should pay attention to safety when using robotic vacuums, such as pulling out power cables of heaters,” an official said.

According to the Tokyo Fire Department’s announcement, an electric heater apparently pushed by a robotic vacuum came into contact with and burnt a sofa in an apartment in December.

The heater was originally placed 50 centimeters from the couch, but the vacuum likely moved it while operating. The resident was in another room at the time.

In another case in February, an electric heater under a desk was pushed by a robotic vacuum into a chest, causing a fire that burned a 20-square-meter area of the apartment.

The resident was out when the vacuum was operating.

The Tokyo Fire Department carried out an experiment and discovered that a robotic vacuum could push an electric heater up to a sofa.

Another experiment showed that a heater's power cord could be caught by a robotic vacuum, resulting in an accidental movement of the heater.