Indonesia issued a tsunami warning on Wednesday after a massive and shallow earthquake struck off the west coast of its island of Sumatra, a region devastated by the 2004 Indian Ocean quake and tsunami, Reuters reports.

The warning was issued for West Sumatra, North Sumatra and Aceh after the quake of magnitude 7.9, the National Meteorological Agency said, but rescue efforts will be hampered by the darkness that falls early in the tropical archipelago.

The epicenter was 808 km southwest of Padang, the U.S. Geological Survey said. It was 10 km deep.

There were no immediate reports of damage or casualties, but the shallower a quake, the more likely it is to cause damage. USGS originally put the magnitude at 8.2, and then 8.1, before lowering it to 7.9.

“So far there have been no reports (of damage) yet,” Andi Eka Sakya, an official of the National Meteorological Agency, told TVOne. “In Bengkulu (on southwest coast of Sumatra) they didn’t feel it at all.”

Neighboring Australia issued a tsunami watch for parts of its western coast.