ALEXANDRIA, Egypt -- The police investigation into a New Year's church bombing that killed 21 people is focusing on a local group of Islamic hard-liners inspired by but not directly linked to Al Qaeda, Egyptian security officials said Sunday.

The attack in the Mediterranean port city of Alexandria struck worshippers as they were leaving midnight Mass Saturday about 30 minutes into the new year and also wounded about 100.

Dozens of grieving Christians returned to pray Sunday in the blood-spattered church, many of them sobbing, screaming in anger and slapping themselves in grief.

In the immediate aftermath of the attack, Egyptian officials have blamed it on foreigners and Al Qaeda, even before they completed an investigation. But on Sunday, security officials said police are looking at the possibility that Islamic hard-liners based in Alexandria were behind the attack, and perhaps were inspired by Al Qaeda but not under a foreign command.

Investigators were also examining lists of air passengers who arrived recently in Egypt from Iraq, where the local Al Qaeda branch has threatened Egyptian Christians. They said they are looking for any evidence of an Al Qaeda financier or organizer who may have visited Egypt to recruit the bomber and his support team from among the ranks of local militants.

The officials, who spoke on condition of anonymity because the investigation has not yet been completed, said 25 people have been detained for questioning, but none of them was thought to be linked to the attack. They said the 25 were mostly owners of cars parked outside the church at the time, storekeepers and Muslim neighbors known to be Islamic fundamentalists.

Egypt's government has long insisted that Al Qaeda does not have a significant presence in the country, and it has never been conclusively linked to any attacks here.

But Egypt does have a rising movement of Islamic hard-liners who, while they do not advocate violence, adhere to an ideology similar in other ways to Al Qaeda. There have been fears they could be further radicalized by sectarian tensions. The hard-liners, known as Salafis, have a large and active presence in Alexandria.