Two men who died in a crash were being pursued by police for less than a minute, the police watchdog has said.
Patrick Connors, 36, and Thomas Sharp, 29, were killed in the crash in Salford, Greater Manchester, on the night of 23 September.
The men were travelling in a Mercedes C class car before it crashed with two other vehicles.
An investigation into the crash is "progressing well," the Independent Office for Police Conduct said.
Initial inquiries have shown that an unmarked police car used its emergency lights and siren to signal to the Mercedes to stop, the IOPC said.
Following a short pursuit, which lasted less than one minute along Lower Broughton Street and Frederick Road, the Mercedes collided with two cars travelling in the opposite direction, the watchdog added.
IOPC regional director Amanda Rowe described the deaths as "a tragic incident".
She said it was mandatory for police to refer the matter to the IOPC.
The watchdog will consider car footage, CCTV and witness statements as part of the inquiry.
The driver of the first car, a VW Passat, was uninjured while a taxi driver in the second car, also a VW Passat, suffered minor injuries.
Two female passengers in the taxi were taken to hospital with serious injuries, not thought to be life-threatening.
An inquest into the two men's deaths has been opened.