Gunmen came to the Dolmande site in Soum province and fired on people working there, killing 20, a security source said on condition of anonymity on Sunday.
A local source said around 20 people had been killed in the attack, but gave no further details.
There was no immediate comment from the Burkinabe authorities.
Once a pocket of relative calm in the Sahel, Burkina has suffered a homegrown insurgency for the past three years, which has been amplified by a spillover of jihadist violence and criminality from its chaotic neighbour Mali.Friday's bloodshed extends a run of recent violence, that includes the death of at least 29 people in attacks on a food convoy and a transport truck in early September.