A senior police official, speaking on condition of anonymity on Saturday, said 20 people were being held, some of them quarry workers who are suspected of having had access to explosives.
Those 20, some or all of them beduins, appeared to be among the dozens to whom security officials had referred.
Three car bombs exploded on Thursday night, one at the Taba Hilton just south of the Egypt-Israel border and two in a town of beach huts, Ras Shitan, 55km to the south on the Red Sea coast.
The Egyptian Interior Ministry said on Saturday that 34 people had been killed in the attacks. It said the dead included five Israelis, nine Egyptians and 20 unidentified bodies.
A total of 105 people were injured.
Searching for leads
Some Israeli officials believe the al-Qaida network was most likely to be behind the attack, while Egyptian authorities say it is too early to point to suspects.
At the half-demolished Taba Hilton on Saturday, forensic investigators searched the rubble for a lead on the identities of the attackers.
The Taba Hilton was attacked
with a car bomb
Fingerprints were lifted from the car thought to have been used in the attack. It is believed to have been packed with 200kg of explosives.
DNA samples were also taken from body parts to determine whether human bombers drove the vehicle.
Egyptian and Israeli rescue teams have been working side by side to salvage bodies from the wreckage of the Taba Hilton.
But as tension simmers between Israel and Egypt over a four-year-old Palestinian uprising, some Egyptians have balked at the influx of Israeli rescue personnel.
"We should not have allowed them here even if it was their dead. Would they have done the same? No way. It shows us as inadequate and it's humiliating," said nurse Yahya Ahmad.