The search for the killers of two police officers on the Jordan Valley's Route 90 Sunday night is continuing, but it has mostly focused on intelligence gathering.

Security forces are convinced that the incident was a terrorist attack, but there is still no clear view as to which group the culprit, or culprits, belonged to.

Monday, Israel Defense Forces sources rejected claims of responsibility by a group called Imad Mughniyeh Battalions, named after the assassinated Hezbollah terrorist mastermind.

Forensic investigators have concluded that the two officers were shot at very close range with a 9mm pistol, and it is believed that this had happened when they stopped their patrol car to assist passengers in a vehicle that they thought was experiencing problems.

According to the police theory, the minute the officers stepped out of their car they were shot, and the assailant, or assailants, fled in their car.

The theory is based on equipment for changing a flat tire found near the patrol car.

"At this time there is no substantial progress in the investigation and we do not know what precisely happened," a senior police officer involved in the investigation said Monday. "All scenarios, including the one that the gunmen had faked car problems are still theoretical. We cannot say who was behind this attack, where they came from and how they surprised the officers, and where they fled to."

The officer added that "even though it is clear to us that the motive behind the attack is nationalist, the evidence we have so far collected does not, from our point of view, allow us to determine that it was not a criminal incident."

One of the officers, Superintendent David Rabinowitz, was laid to rest at the Haifa cemetery. Hundreds of civilians and police officers were in attendance.

Police Commissioner David Cohen spoke at the funeral and referred to the two dead officers as "heroes who gave their life to protect the country."