Hundreds more remain in hospital.
Sri Lanka's junior defense minister has blamed breakaway members of two obscure local extremist Muslim groups, and said numerous suicide bombers were highly educated and came from well-off families.
"Their thinking is that Islam can be the only religion in this country", he told reporters.
Mr Wijewardene said that "most of [the attackers] are well educated and come from. middle or upper middle class" families.
ISIS released the names of the 7 terrorists who perpetrated the attack; Abu "Ubaida, Abu Al-Mukhtar, Abu Khalil, Abu Hamza, Abu Al-Bara", Abu Muhammad, and Abu Abdallah who perpetrated the attacks.
BBC: "Sri Lanka attacks: "International network" linked to bombings" - "A wave of bombings that killed 290 people in Sri Lanka on Sunday was carried out with the support of an worldwide network, officials said".
He said that one of the nine bombers was a woman.
Sixty suspects have been arrested over the blasts so far.
Ambassador Teplitz said that as the investigation into Sunday's ISIS-claimed attack continued, a team of both FBI agents and USA. military personnel were in Sri Lanka assisting the probe.
Zahran's name was on one intelligence warning shared among Sri Lankan security forces, who apparently even quietly took their growing concerns to global experts as well.
He added that all suspects have some link to the attackers - who he refused to formally identify.
Amid the frantic hunt for suspects, ISIS claimed responsibility for the strikes and released photos and video of the men it said took part or organized the attacks.
On Wednesday, among many revelation to foreign agencies, Sri Lanka Defence Minister Ruwan Wijewardene said that leader of a local extremist group was also behind the attack.
He added that the attacks were carried out not by the National Tawheed Jamath but by a splinter group, adaderana.lk reported.
Teplitz declined to discuss whether USA officials knew about National Towheed Jamaat or its leader before the attack. "We are trying to apprehend them", he said. She exploded herself along with her two children and police moved in to search a house they were in, in the aftermath of the attacks, Gunasekara said. No bomb was found in the motorcycle.
ISIS had earlier claimed responsibility for the suicide bombings which led to the deaths of over 300 persons, saying it targeted Christians and Sri Lanka citizens.
"Indian intelligence officers contacted their Sri Lankan counterparts two hours before the first attack to warn of a specific threat on churches", one Sri Lankan defence source and an Indian government source told Reuters.
"I will completely restructure the police and security forces in the coming weeks".
He also said the government had evidence the bombings were carried out by an Islamic fundamentalist group in retaliation for the 15 March mosque shootings in Christchurch that killed 50 people.
PM Jacinda Ardern has responded to the suggestion that the Sri Lanka bombings were retaliation for the Christchurch attacks.
She also called on everyone to pray for Sri Lanka, and the world in general, so that love and peace, and not terror and violence, be the choice in life.
The diplomats - including Turkish Ambassador Tunca Ozcuhadar - paid a visit to Cardinal Malcolm Ranjith to pledge solidarity with the Christian community in Sri Lanka.