Doctors treated patients in tents set up under a scorching Philippine sun on Tuesday ¡ª including helping a young mother give birth ¡ª as the death toll from a major earthquake that collapsed buildings topped 40.

Thousands remained displaced and more than 450 injured following the magnitude-7.8 quake that struck off the southern island of Mindanao on Monday, according to national and local disaster agencies, with four people now believed missing.

In hardest-hit Sarangani province, some areas remain accessible only by helicopter while fears of aftershocks were slowing rescue efforts, local officials told reporters at a Tuesday briefing.