A pregnant teenager and her husband are understood to be the two burglary suspects who died after their car smashed into a coach as they were chased by police.
Newlyweds Patrick McDonagh, 19, and his 18-year-old wife Shauna, were killed on the A40 near East Acton in west London at about 9pm on Sunday.
The couple, who wed last year, were said to be expecting a baby girl in April. The unborn child is not believed to have survived the crash.
Hundreds of tributes to the young couple have been posted on social media from friends and family.
A second man who was in the car was taken to hospital and has subsequently been arrested on suspicion of aggravated burglary.
Around 20 minutes before the fatal collision police had been called to reports of an aggravated burglary in Harrow and began a high-speed road chase.
During the pursuit the suspects' car veered to the wrong side of the A40 near the junction with Kingsdown Avenue and crashed into a coach.
Watchdog the Independent Office for Police Conduct and the Metropolitan Police internal Directorate of Professional Standards have been informed.