Police say it appeared Dykes, who was due to fly home for Christmas on Saturday, had been strangled. An initial post-mortem examination was conducted, but an official cause of death was not revealed. A second examination has been scheduled.
Local officials have claimed she was raped, however, this has not been confirmed.
Dykes who had been working in Beirut since January 2017, had been at a going-away party for a colleague in the popular Gemmayzeh district of Beirut.
Officers believe the policy manager for the Department for International Development (DfID) was abducted after leaving a bar. Her body was found close to the Metn highway, on the eastern outskirts of the Lebanese capital.
Her family said in a statement: “We are devastated by the loss of our beloved Rebecca. We are doing all we can to understand what happened.”
A DfID spokesman said: “Our thoughts are with Becky’s family and friends at this very upsetting time.”
The Foreign Office said it was in contact with the Lebanese authorities following the death of a British woman in Beirut. Police are describing the death as a “criminal act” but say it was not politically motivated.