The Sri Lankan Police on Wednesday said they have not found enough evidence to prove Islamic State group militants were involved in the Easter Sunday bombings on April 21 that killed more than 250 people, Reuters reported.

The Islamic State group had claimed responsibility for the serial bomb blasts. However, the group did not provide any evidence of its involvement. Sri Lankan investigators have blamed an Islamist organisation called the National Thowheed Jamath for the serial bomb blasts.

“From the investigations conducted so far there is not enough evidence to say that there is a direct ISIS link to the Easter Sunday attacks,” Ravi Seneviratne, the head of the Criminal Investigations Department, told a parliament select committee probing the bombings.

“They followed the IS ideology, but our investigations have not shown any link between them,” Seneviratne was quoted as saying by AFP. He noted that two days after the blasts, remnants of the NTJ had convinced the Islamic State group to claim the blasts.

Another investigator, Shani Abeysekara, told the same parliamentary committee that the CID had found 105 kilograms (230 pounds) of explosives from a NTJ hideout earlier this year.

NTJ leader Zahran Hashim had made a video with his fellow suicide bombers pledging allegiance to IS leader Abu Bakr Al-Bagdadi. The video was released by the Islamic State group two days later.

On Monday, the government had extended the state of emergency by another month to maintain “public security” in the country. The state of emergency was first imposed following serial bombings in Sri Lanka on April 21. It was renewed on May 22, then again on June 22, and was set to expire on Monday.

The Sri Lankan Police have arrested over 1,000 suspects following the attacks. Police officials claimed that all those responsible for the blasts have either been killed or arrested. However, the investigations into the suicide bombings at the three churches and three luxury hotels are still underway.

On July 9, the Sri Lankan magistrates’ court had granted bail to the country’s police chief and its former defence secretary in connection with the Easter attacks. They were first two state officials to be arrested for allegedly failing to prevent the bombings.