A fifth force between dark matter particles has been advocated as explanation of many astrophysical anomalies and of the $g-2$ discrepancy.
The KLOE Collaboration searched for the mediator of such dark force, the dark photon, and set six constraints on the dark force coupling strength $\varepsilon^2$, by investigating the $\phi$-Dalitz decay into the $\eta$ meson, the dark photon production from continuum, and the Higgsstrahlung process.
New analyses will profit of the KLOE-2 data, which will allow to improve the sensitivity of all exploited processes by a factor of 2, thanks to the larger statistical sample and to the upgraded tracking detector.