Detectives from Scotland Yard's counter-terrorism team travelled to Libya today as part of the investigation into the murder of policewoman Yvonne Fletcher, the force said.
Two officers flew to Tripoli after authorities in the country asked them to come back to Libya as soon as possible.
They are due to meet officials to continue discussions about working together on the investigation, the Met said.
Wpc Fletcher was killed outside the Libyan embassy in London during a demonstration in 1984.
She was shot and fatally injured by someone who fired from inside the building.
Scotland Yard said Libyan officials last week asked them to return to the country as soon as they could.
It is hoped that the officers, who are expected to be in Tripoli for several days, can meet with the country's prosecutor general.
Wpc Fletcher's family will be kept updated about the visit, Scotland Yard said.
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