At least three Britons are believed to have been on board Germanwings flight 4U9525, the foreign secretary Philip Hammond has confirmed.
Initial reports suggest the victims were mother and her seven-month-old baby from Manchester and a father of two from Wolverhampton.
"We currently believe three British people have been killed, but we can’t rule out the possibility that there are more involved," Hammond said this morning. "We are in contact with the families of those known to be killed, and we are also in touch which the French, German and Spanish authorities."
The rescue mission resumed this morning, in the hope of finding the crucial second black box.
The first black box was discovered in the crash site, in the French Alps, yesterday afternoon. The cockpit voice recorder recovered from the wreckage has been found damaged and has been taken to Paris for analysis.
Officials say it is critical they are found in order to understand why the Airbus A320, operated by Lufthansa's budget arm Germanwings, entered a rapid eight-minute descent during its journey between Barcelona and Duesseldorf.
No distress signal was sent and the crew failed to respond to desperate attempts at contact from ground control.
Investors appear no closer to answering what caused the crash. France's interior minister Bernard Cazeneuve said this morning: "Terrorism theory is not the theory we're focusing on."
Weather was calm at the time, according to French officials. Lufthansa said it was working on the assumption that the crash was an "accident".
"Anything else would be speculation," Lufthansa vice president Heike Birlenbach told reporters in Barcelona.