The Rail Accident Investigation Branch (RAIB) has appealed for witnesses who may have any information related to the Croydon tram crash which killed seven people on Wednesday.
RAIB inspector, Ian Capewell, added that an interim report on the possible reasons for the crash would be published next week.
He said the agency would like to talk to people who were on the derailed tram or from anyone who regularly travels on the tram route, works on the tram or people who live nearby.
Mr Capewell said the investigation is ongoing and RAIB inspectors would stay on site at least until Saturday.
Six men and one woman died when a tram derailed in Croydon
A teenager described as a "friendly, genuine lad" has been named among the seven people killed when a tram derailed in Croydon.
The driver of a tram that derailed killing seven has been questioned amid suggestions it failed to break before taking a corner at speed.