Grieving relatives are trying to help identify the remains of the 153 people killed when a Spanish plane veered off a runway and burst into flames, while investigators try to determine the cause.

Officials moved many of the badly burned bodies Thursday to a makeshift morgue at a Madrid convention center.

Spain's Development Minister, Magdalena Alvarez, says it could take two days to identify most of the victims. She says investigators will have to use DNA testing in some cases.

The Spanair plane was carrying 172 people when it burst into flames shortly after takeoff Wednesday at Madrid airport. Officials say most of the passengers were Spanish. The dead included citizens from 10 other countries (Germany, France, Mauritania, Turkey, Brazil, Indonesia, Bulgaria, Italy, Colombia and Gambia).

Nineteen people, including some children, survived the crash.

Spain is observing three days of mourning following the country's worst air disaster in more than two decades.

Investigators say the pilot initially reported a problem with a temperature gauge, delaying takeoff while mechanics resolved the problem.

Authorities say they have recovered the aircraft's two black box (flight data) recorders, which could help determine what caused the crash. Investigators have already ruled out foul play.

The MD-82 aircraft was bound for the Canary Islands, a popular tourist destination.

Some information for this report was provided by AFP, AP and Reuters.