The main gas pipeline sending supplies from Egypt to Jordan and Israel has been attacked, causing two large explosions, Egyptian officials say.
The blasts happened near the town of al-Arish in the north of the Sinai desert, sending flames high into the air, witnesses and local media say.
There have been frequent attacks on gas pipelines in the Sinai since the overthrow of President Hosni Mubarak.
Egypt sends nearly half its gas to Israel, in a much-criticised agreement.
Witnesses said two large explosions happened close together after six men arrived in an unmarked vehicle.
The area has seen increasing unrest, partly due to tensions with heavily-armed Bedouin tribes who live there.
The pipeline had only been repaired last week after it was shut down on 5 February by a previous explosion.
Security officials say there have been at least 12 attacks on pipelines since President Mubarak was deposed in February 2011.