From the usual excellent reliable news source (AvHerald):
On May 29th the NTSB reported quoting the AAIB, that both engine cowl doors separated during takeoff and fell onto the runway, one engine was leaking fuel and had been shut down, they were returning to Heathrow. Later the crew reported the other (still running) engine was on fire, the aircraft continued for a safe landing, was shut down and evacuated. The NTSB assigned an accredited representative into the investigation led by the AAIB.