In an audio statement issued by the defense ministry on Monday, acting police chief Chandana Wickramaratne said almost all suspects and plotters involved in the April 21 attacks had either been arrested or were dead.

“There were also two people among that group of plotters who are experts in bombs and those two are dead now,” Wickramarate said. “They had stored part of the explosives for future attacks and we have confiscated all of this.”

Investigators are still tracking down 10 more key players associated with plotting the bombings, which killed more than 250 people, including 42 foreigners, a military source told Reuters on Tuesday.

“The investigations show there were another 8 to 10 people who attended meetings with the other plotters,” the source said.

Assets worth about US$40 million belonging to the bombers and plotters linked to the April 21 attacks have been frozen, police spokesman Ruwan Gunesekera said.

Sri Lankan authorities have said the bombings were believed to have been carried out by two little-known domestic Islamist groups, the National Tawheed Jamaath (NTJ) and Jamathei Millathu Ibrahim (JMI). Islamic State has claimed responsibility.

Investigators from eight countries, including the US Federal Bureau of Investigation and Interpol, are helping Sri Lanka with the investigation.

In focus are whether the plotters had any foreign help, the sources of funding and if the bombers had any credible link to Islamic State.

Sri Lankan President Maithripala Sirisena told Reuters over the weekend that all indications pointed to Islamic State involvement.